sql复制代码CREATE TABLE hero (
    number INT,
    name VARCHAR(100),
    country varchar(100),
    PRIMARY KEY (number),
    KEY idx_name (name)
) Engine=InnoDB CHARSET=utf8;

sql复制代码INSERT INTO hero VALUES
    (1, 'l刘备', '蜀'),
    (3, 'z诸葛亮', '蜀'),
    (8, 'c曹操', '魏'),
    (15, 'x荀彧', '魏'),
    (20, 's孙权', '吴');

sql复制代码SELECT * FROM hero WHERE name <=  'l刘备' AND country = '魏';

sql复制代码SELECT * FROM hero WHERE name < 'l刘备' OR name > 'x荀彧';

ini复制代码SELECT * FROM hero WHERE name = 'l刘备' AND country = '魏';

sql复制代码SELECT * FROM hero WHERE name <=  'l刘备' AND country = '魏';

sql复制代码SELECT * FROM hero WHERE name < 's孙权' AND country = '魏' ORDER BY name DESC FOR UPDATE ;

sql复制代码SELECT * FROM hero WHERE name = 's孙权' FOR UPDATE;

sql复制代码SELCT * FROM hero WHERE number >= 8 FOR UPDATE;

ini复制代码public class PropertySourceBootstrapConfiguration implements
        ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {
 
  @Autowired(required = false)
    private List<PropertySourceLocator> propertySourceLocators = new ArrayList<>();
 
   // ......
  @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        List<PropertySource<?>> composite = new ArrayList<>();
        AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
        boolean empty = true;
    // 从应用上下文中，取出环境类
        ConfigurableEnvironment environment = applicationContext.getEnvironment();
        for (PropertySourceLocator locator : this.propertySourceLocators) {
      // 执行 locateCollection 方法，获取具体配置。
      // 注意本方法执行后，配置已经被从远程加载进来了。
            Collection<PropertySource<?>> source = locator.locateCollection(environment);
            // ....
            List<PropertySource<?>> sourceList = new ArrayList<>();
            for (PropertySource<?> p : source) {
                if (p instanceof EnumerablePropertySource) {
                    EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) p;
                    sourceList.add(new BootstrapPropertySource<>(enumerable));
                }
                // ....
            }
            composite.addAll(sourceList);
            empty = false;
        }
        if (!empty) {
            MutablePropertySources propertySources = environment.getPropertySources();
            // ....
      // 把 composite(远程的属性) 设置到 环境类中
            insertPropertySources(propertySources, composite);
            // ....
        }
    }
 
  // .....
}

scss复制代码public interface PropertySourceLocator {
 
    PropertySource<?> locate(Environment environment);
 
    default Collection<PropertySource<?>> locateCollection(Environment environment) {
        return locateCollection(this, environment);
    }
  // 注意，上文 PropertySourceBootstrapConfiguration # initialize，调用了此方法。
  // 也就是调用了 locate 方法。
    static Collection<PropertySource<?>> locateCollection(PropertySourceLocator locator,
            Environment environment) {
        PropertySource<?> propertySource = locator.locate(environment);
    // ....
    }
 
}

arduino复制代码public class NacosPropertySourceLocator implements PropertySourceLocator {
 
  @Override
    public PropertySource<?> locate(Environment env) {
        // ....
 
        CompositePropertySource composite = new CompositePropertySource(
                NACOS_PROPERTY_SOURCE_NAME);
 
    // 1.加载共享配置
        loadSharedConfiguration(composite);
    // 2.加载扩展配置
        loadExtConfiguration(composite);
    // 3.加载应用配置
        loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);
 
        return composite;
    }
 
  // 1、2、3底层都是通过调用 loadNacosDataIfPresent
    private void loadNacosDataIfPresent(final CompositePropertySource composite,
        final String dataId, final String group, String fileExtension,
        boolean isRefreshable) {
    // ....
    NacosPropertySource propertySource = this.loadNacosPropertySource(dataId, group,
            fileExtension, isRefreshable);
    this.addFirstPropertySource(composite, propertySource, false);
}
 
  // 继续调用 loadNacosPropertySource()
  private NacosPropertySource loadNacosPropertySource(final String dataId,
            final String group, String fileExtension, boolean isRefreshable) {
    // 不自动刷新，直接从本地缓存拿
        if (NacosContextRefresher.getRefreshCount() != 0) {
            if (!isRefreshable) {
                return NacosPropertySourceRepository.getNacosPropertySource(dataId,
                        group);
            }
        }
    // 这里是发请求的方法
        return nacosPropertySourceBuilder.build(dataId, group, fileExtension,
                isRefreshable);
    }
}

typescript复制代码public class NacosPropertySourceBuilder {
 
    NacosPropertySource build(String dataId, String group, String fileExtension,
            boolean isRefreshable) {
        Map<String, Object> p = loadNacosData(dataId, group, fileExtension);
        NacosPropertySource nacosPropertySource = new NacosPropertySource(group, dataId,
                p, new Date(), isRefreshable);
        NacosPropertySourceRepository.collectNacosPropertySource(nacosPropertySource);
        return nacosPropertySource;
    }
 
    private Map<String, Object> loadNacosData(String dataId, String group,
            String fileExtension) {
        String data = null;
        try {
      // 获取配置。重点。
            data = configService.getConfig(dataId, group, timeout);
            // 格式化配置
            Map<String, Object> dataMap = NacosDataParserHandler.getInstance()
                    .parseNacosData(data, fileExtension);
            return dataMap == null ? EMPTY_MAP : dataMap;
        }
        return EMPTY_MAP;
    }
}

vbnet复制代码public class NacosConfigService implements ConfigService {
 
    @Override
    public String getConfig(String dataId, String group, long timeoutMs) throws NacosException {
        return getConfigInner(namespace, dataId, group, timeoutMs);
    }
 
  private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {
        group = blank2defaultGroup(group);
        ParamUtils.checkKeyParam(dataId, group);
        ConfigResponse cr = new ConfigResponse();
        cr.setDataId(dataId);
        cr.setTenant(tenant);
        cr.setGroup(group);
 
            // ...
 
        try {
            // 从远程获取配置信息。content 字符串的内容就是具体的配置内容。
            ConfigResponse response = worker.getServerConfig(dataId, group, tenant, timeoutMs, false);
            cr.setContent(response.getContent());
            cr.setEncryptedDataKey(response.getEncryptedDataKey());
            configFilterChainManager.doFilter(null, cr);
            content = cr.getContent();
            return content;
        } catch (NacosException ioe) {
            // ...
        }
        // ...
    }
}

java复制代码public class Service {

    public void doMethod(int condition) {
       if (conditionA) {
    		   // 逻辑A
       } else if (conditionB) {
           // 逻辑B
       } else if (conditionC) {
           // 逻辑C
       } else {
           // 逻辑D
       }
    }
}

java复制代码public interface Strategy {
    void method();
}

public class StrategyA implements Strategy {
    @Override
    public void method() {
		// 逻辑A
    }
}

public class StrategyB implements Strategy {
    @Override
    public void method() {
        // 逻辑B
    }
}

public class StrategyC implements Strategy {
    @Override
    public void method() {
		// 逻辑C
    }
}

public class StrategyD implements Strategy {
    @Override
    public void method() {
		// 逻辑D
    }
}

public class StrategyFactory   {
    
    private Strategy strategy;
   
    public Strategy getStrategyByCondition(int condition) {
        // 根据条件返回不同的 strategy
    }
}


public class Service {

    StrategyFactory strategyFactory;

    public void doMethod(int condition) {
        Strategy strategy = strategyFactory.getStrategyByCondition(condition);
        strategy.method();
    }
}

java复制代码ThreadPoolExecutor pool = new ThreadPoolExecutor(
        /*...省略 ...*/
         new ThreadPoolExecutor.AbortPolicy());

ThreadPoolExecutor pool = new ThreadPoolExecutor(
        /*...省略 ...*/
         new ThreadPoolExecutor.DiscardOldestPolicy());

java复制代码@Component
public class FormSubmitHandlerFactory implements InitializingBean, ApplicationContextAware {

    private static final
    Map<String, FormSubmitHandler<Serializable>> FORM_SUBMIT_HANDLER_MAP = new HashMap<>(8);

    private ApplicationContext appContext;

    /**
     * 根据提交类型获取对应的处理器
     *
     * @param submitType 提交类型
     * @return 提交类型对应的处理器
     */
    public FormSubmitHandler<Serializable> getHandler(String submitType) {
        return FORM_SUBMIT_HANDLER_MAP.get(submitType);
    }

    @Override
    public void afterPropertiesSet() {
        // 将 Spring 容器中所有的 FormSubmitHandler 注册到 FORM_SUBMIT_HANDLER_MAP
        appContext.getBeansOfType(FormSubmitHandler.class)
                  .values()
                  .forEach(handler -> FORM_SUBMIT_HANDLER_MAP.put(handler.getSubmitType(), handler));
    }

    @Override
    public void setApplicationContext(@NonNull ApplicationContext applicationContext) {
        appContext = applicationContext;
    }
}

java复制代码@Configuration
public class StrategyConfig implements ApplicationContextAware, InitializingBean {

    private ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // 配置 StrategyFactory 和 Strategy Bean
    }
}

java复制代码/**
 * 泛型 Strategy 接口
 * @author shimengjie
 * @date 2021/11/5 14:39
 **/
public interface Strategy<K> {

    /**
     * 返回类型
     *
     * @return K
     */
    K getType();
}

/**
 * 泛型 StrategyFactory 接口
 *
 * @author shimengjie
 * @date 2021/11/5 14:41
 **/
public interface StrategyFactory<K> {

    /**
     * 添加 Strategy 实例
     *
     * @param k Strategy 的类型
     * @param v Strategy 实例
     */
    void addStrategy(K k, Strategy<K> v);

    /**
     * 根据 key 值取出对应的 Strategy
     *
     * @param key Strategy 的类型
     * @return Strategy 实例
     */
    Strategy<K> getByType(K key);
}

java复制代码@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface RegistryStrategyFactory {

    /**
     * 指定策略实现类
     */
    Class<? extends Strategy> strategy();
}

java复制代码public interface WorkStrategy extends Strategy<String> {

    /**
     * 判断作品是否存在
     *
     * @param id 作品ID
     * @return true/false
     */
    boolean isExisted(Long id);
}

@Component
@RegistryStrategyFactory(strategy = WorkStrategy.class)
public class WorkStrategyFactory implements StrategyFactory<String> {

    /**
     * 保存 WorkStrategy 实例
     */
    private Map<String, WorkStrategy> map;

    public WorkStrategyFactory() {
        this.map = new HashMap<>();
    }

    @Override
    public void addStrategy(String k, Strategy<String> v) {
        map.put(k, (WorkStrategy) v);
    }

    @Override
    public WorkStrategy getByType(String key) {
        return map.get(key);
    }
}

java复制代码@Override
public void afterPropertiesSet() throws Exception {
    // 便利注册的 StrategyFactory
    for (StrategyFactory factory : applicationContext.getBeansOfType(StrategyFactory.class).values()) {
        RegistryStrategyFactory annotation = AnnotationUtils.findAnnotation(factory.getClass(), RegistryStrategyFactory.class);
        if (annotation != null) {
            // 取出注解中指定的 策略 Bean
            Class<? extends Strategy> strategyClazz = annotation.strategy();
            Map<String, ? extends Strategy> map = applicationContext.getBeansOfType(strategyClazz);
            // 添加进 map 中
            for (Strategy value : map.values()) {
                factory.addStrategy(value.getType(), value);
            }
        }
    }
}

java复制代码
public interface IEmployee {
    void doing(String task);
}

java复制代码
public class EmployeeA implements IEmployee {
    protected String goodAt = "编程";
    public void doing(String task) {
        System.out.println("我是员工A，我擅长" + goodAt + ",现在开始做" +task + "工作");
    }
}

java复制代码
public class EmployeeB implements IEmployee {
    protected String goodAt = "平面设计";
    public void doing(String task) {
        System.out.println("我是员工B，我擅长" + goodAt + ",现在开始做" +task + "工作");
    }
}

java复制代码
public class Leader implements IEmployee {

    private Map<String,IEmployee> employee = new HashMap<String,IEmployee>();

    public Leader(){
        employee.put("爬虫",new EmployeeA());
        employee.put("海报图",new EmployeeB());
    }

    public void doing(String task) {
        if(!employee.containsKey(task)){
            System.out.println("这个任务" +task + "超出我的能力范围");
            return;
        }
        employee.get(task).doing(task);
    }
}

java复制代码
public class Boss {
    public void command(String task,Leader leader){
        leader.doing(task);
    }
}

java复制代码
public class Test {
    public static void main(String[] args) {
        new Boss().command("海报图",new Leader());
        new Boss().command("爬虫",new Leader());
        new Boss().command("卖手机",new Leader());
    }
}

java复制代码
public abstract class ClassLoader {
    ...
    private final ClassLoader parent;
    ...
    protected Class<?> loadClass(String name, boolean resolve)
        throws ClassNotFoundException
    {
        synchronized (getClassLoadingLock(name)) {
              Class<?> c = findLoadedClass(name);
            if (c == null) {
                long t0 = System.nanoTime();
                try {
                    if (parent != null) {
                        c = parent.loadClass(name, false);
                    } else {
                        c = findBootstrapClassOrNull(name);
                    }
                } catch (ClassNotFoundException e) {
                }

                if (c == null) {
                    long t1 = System.nanoTime();
                    c = findClass(name);

                    sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);
                    sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
                    sun.misc.PerfCounter.getFindClasses().increment();
                }
            }
            if (resolve) {
                resolveClass(c);
            }
            return c;
        }
    }
    ...
}

java复制代码
public Object invoke(Object obj, Object... args)
        throws IllegalAccessException, IllegalArgumentException,
           InvocationTargetException
    {
        if (!override) {
            if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
                Class<?> caller = Reflection.getCallerClass();
                checkAccess(caller, clazz, obj, modifiers);
            }
        }
        MethodAccessor ma = methodAccessor;             // read volatile
        if (ma == null) {
            ma = acquireMethodAccessor();
        }
        return ma.invoke(obj, args);
}

java复制代码
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
   //判断节点是否属于同一命名空间，如果是，则执行后续的解析
   if (delegate.isDefaultNamespace(root)) {
      NodeList nl = root.getChildNodes();
      for (int i = 0; i < nl.getLength(); i++) {
         Node node = nl.item(i);
         if (node instanceof Element) {
            Element ele = (Element) node;
            if (delegate.isDefaultNamespace(ele)) {
               parseDefaultElement(ele, delegate);
            }
            else {
               //注解定义的Context的nameSpace进入这个分支
               delegate.parseCustomElement(ele);
            }
         }
      }
   }
   else {
      delegate.parseCustomElement(root);
   }
}

java复制代码
/**
 * Created by Tom.
 */
public class MemberController {

    public void getMemberById(String mid){

    }

}

java复制代码
/**
 * Created by Tom.
 */
public class OrderController {

    public void getOrderById(String mid){

    }

}

java复制代码
/**
 * Created by Tom.
 */
public class SystemController {

    public void logout(){

    }
}

java复制代码
public class DispatcherServlet extends HttpServlet {

    private Map<String,Method> handlerMapping = new HashMap<String,Method>();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doDispatch(req,resp);
    }

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) {
        String url = req.getRequestURI();
        Method method = handlerMapping.get(url);
	   //此处省略反射调用方法的代码
		   ...
		
    }

    @Override
    public void init() throws ServletException {
        try {
            handlerMapping.put("/web/getMemeberById.json", MemberController.class.getMethod("getMemberById", new Class[]{String.class}));
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

java复制代码
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:javaee="http://java.sun.com/xml/ns/javaee"
   xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
   version="2.4">
   <display-name>Web Application</display-name>


   <servlet>
      <servlet-name>delegateServlet</servlet-name>
      <servlet-class>com.tom.pattern.delegate.mvc.DispatcherServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
   </servlet>

   <servlet-mapping>
      <servlet-name>delegateServlet</servlet-name>
      <url-pattern>/*</url-pattern>
   </servlet-mapping>

</web-app>

scss复制代码stringRedisTemplate.watch(key);
stringRedisTemplate.multi();

stringRedisTemplate.opsForValue().set
stringRedisTemplate.exec();

rust复制代码输入：board = "WRRBBW", hand = "RB"

输出：-1

解释：无法移除桌面上的所有球。可以得到的最好局面是：
- 插入一个 'R' ，使桌面变为 WRRRBBW 。WRRRBBW -> WBBW
- 插入一个 'B' ，使桌面变为 WBBBW 。WBBBW -> WW
桌面上还剩着球，没有其他球可以插入。

rust复制代码输入：board = "WWRRBBWW", hand = "WRBRW"

输出：2

解释：要想清空桌面上的球，可以按下述步骤：
- 插入一个 'R' ，使桌面变为 WWRRRBBWW 。WWRRRBBWW -> WWBBWW
- 插入一个 'B' ，使桌面变为 WWBBBWW 。WWBBBWW -> WWWW -> empty
只需从手中出 2 个球就可以清空桌面。

php复制代码输入：board = "G", hand = "GGGGG"

输出：2

解释：要想清空桌面上的球，可以按下述步骤：
- 插入一个 'G' ，使桌面变为 GG 。
- 插入一个 'G' ，使桌面变为 GGG 。GGG -> empty
只需从手中出 2 个球就可以清空桌面。

rust复制代码输入：board = "RBYYBBRRB", hand = "YRBGB"

输出：3

解释：要想清空桌面上的球，可以按下述步骤：
- 插入一个 'Y' ，使桌面变为 RBYYYBBRRB 。RBYYYBBRRB -> RBBBRRB -> RRRB -> B
- 插入一个 'B' ，使桌面变为 BB 。
- 插入一个 'B' ，使桌面变为 BBB 。BBB -> empty
只需从手中出 3 个球就可以清空桌面。

Java复制代码class Solution {
    int INF = 0x3f3f3f3f;
    String b;
    int m;
    Map<String, Integer> map = new HashMap<>();
    public int findMinStep(String a, String _b) {
        b = _b;
        m = b.length();
        int ans = dfs(a, 1 << m);
        return ans == INF ? -1 : ans;
    }
    int dfs(String a, int cur) {
        if (a.length() == 0) return 0;
        if (map.containsKey(a)) return map.get(a);
        int ans = INF;
        int n = a.length();
        for (int i = 0; i < m; i++) {
            if (((cur >> i) & 1) == 1) continue;
            int next = (1 << i) | cur;
            for (int j = 0; j <= n; j++) {
                boolean ok = false;
                if (j > 0 && j < n && a.charAt(j) == a.charAt(j - 1) && a.charAt(j - 1) != b.charAt(i)) ok = true;
                if (j < n && a.charAt(j) == b.charAt(i)) ok = true;
                if (!ok) continue;
                StringBuilder sb = new StringBuilder();
                sb.append(a.substring(0, j)).append(b.substring(i, i + 1));
                if (j != n) sb.append(a.substring(j));
                int k = j;
                while (0 <= k && k < sb.length()) {
                    char c = sb.charAt(k);
                    int l = k, r = k;
                    while (l >= 0 && sb.charAt(l) == c) l--;
                    while (r < sb.length() && sb.charAt(r) == c) r++;
                    if (r - l - 1 >= 3) {
                        sb.delete(l + 1, r);
                        k = l >= 0 ? l : r; 
                    } else {
                        break;
                    }
                }
                ans = Math.min(ans, dfs(sb.toString(), next) + 1);
            }
        }
        map.put(a, ans);
        return ans;
    }
}

Java复制代码class Node {
    // 当前的棋盘状况
    String a;
    // cur 代表当前 hand 的使用情况（若 cur 二进制表示中的第 k 位为 1，代表 hand 的第 k 个彩球已被使用）
    // val 代表「当前棋盘为 a」和「hand 使用情况为 cur」的情况下，至少还需要多少步才能将 a 全部消掉（启发式估算值）
    // step 代表当前局面是经过多少步而来
    int cur, val, step;
    Node (String _a, int _c, int _v, int _s) {
        a = _a;
        cur = _c; val = _v; step = _s;
    }
}

Java复制代码class Solution {
    class Node {
        String a;
        int cur, val, step;
        Node (String _a, int _c, int _v, int _s) {
            a = _a;
            cur = _c; val = _v; step = _s;
        }
    }
    int f(String a, int k) {
        Map<Character, Integer> m1 = new HashMap<>(), m2 =  new HashMap<>();
        for (int i = 0; i < a.length(); i++) {
            m1.put(a.charAt(i), m1.getOrDefault(a.charAt(i), 0) + 1);
        }
        for (int i = 0; i < m; i++) {
            if (((k >> i) & 1) == 0) m2.put(b.charAt(i), m2.getOrDefault(b.charAt(i), 0) + 1);
        }
        int ans = 0;
        for (char c : m1.keySet()) {
            int c1 = m1.get(c), c2 = m2.getOrDefault(c, 0);
            if (c1 + c2 < 3) return INF;
            if (c1 < 3) ans += (3 - c1);
        }
        return ans;
    }

    int INF = 0x3f3f3f3f;
    String b;
    int m;
    Map<String, Integer> map = new HashMap<>();
    public int findMinStep(String _a, String _b) {
        b = _b;
        m = b.length();
        PriorityQueue<Node> q = new PriorityQueue<>((o1,o2)->(o1.val+o1.step)-(o2.val+o2.step));
        q.add(new Node(_a, 1 << m, f(_a, 1 << m), 0));
        map.put(_a, 0);
        while (!q.isEmpty()) {
            Node poll = q.poll();
            String a = poll.a;
            int cur = poll.cur;
            int step = poll.step;
            int n = a.length();
            for (int i = 0; i < m; i++) {
                if (((cur >> i) & 1) == 1) continue;
                int next = (1 << i) | cur;
                for (int j = 0; j <= n; j++) {
                    boolean ok = false;
                    if (j > 0 && j < n && a.charAt(j) == a.charAt(j - 1) && a.charAt(j - 1) != b.charAt(i)) ok = true;
                    if (j < n && a.charAt(j) == b.charAt(i)) ok = true;
                    if (!ok) continue;
                    StringBuilder sb = new StringBuilder();
                    sb.append(a.substring(0, j)).append(b.substring(i, i + 1));
                    if (j != n) sb.append(a.substring(j));
                    int k = j;
                    while (0 <= k && k < sb.length()) {
                        char c = sb.charAt(k);
                        int l = k, r = k;
                        while (l >= 0 && sb.charAt(l) == c) l--;
                        while (r < sb.length() && sb.charAt(r) == c) r++;
                        if (r - l - 1 >= 3) {
                            sb.delete(l + 1, r);
                            k = l >= 0 ? l : r; 
                        } else {
                            break;
                        }
                    }
                    String nextStr = sb.toString();
                    if (nextStr.length() == 0) return step + 1;
                    if (f(nextStr, next) == INF) continue;
                    if (!map.containsKey(nextStr) || map.get(nextStr) > step + 1) {
                        map.put(nextStr, step + 1);
                        q.add(new Node(nextStr, next, f(nextStr, next), step + 1));
                    }
                }
            }
        }
        return -1;
    }
}

csharp复制代码public interface Drink{
    void getName();
}

typescript复制代码public class Coffee implements Drink{
    @Override
    public void getName(){
        System.out.println("Drink: Coffee");
    }
}
​
public class Tea implements Drink{
    @Override
    public void getName(){
        System.out.println("Drink: Tea");
    }
}

java复制代码public interface DrinkDecorator extends Drink{
    
    private Drink drink;
    
    public DrinkDecorator(Drink  drink){
        this.drink = drink;
    }
    
    @Override
    public void getName(){
        drink.getName();
    }
}

scala复制代码public class MilkDecorator extends DrinkDecorator{
    
    public MilkDecorator(Drink  drink) {
        super(drink);
    }
    public void getName() {
        super.getName();
        setMilk();
    }
    public void setMilk() {
        System.out.println("setMilk");
    }
}

csharp复制代码public class DecoratorDemo {
   public static void main(String[] args) {
       
       System.out.println("drink latte");
       Drink latte = new MilkDecorator(new Coffee());
       latte.getName();
       
       System.out.println("drink milky tea");
       Drink milkyTea = new MilkDecorator(new Tea());
       milkyTea.getName();
   }
}

python复制代码my_string = "Hi Python..!"
print(my_string * 2)
#Hi Python..!Hi Python..!
print(my_string + " I love Python" * 2)
#Hi Python..! I love Python I love Python

python复制代码my_string = "Hi Python..!"
print(my_string[::-1])
# !..nohtyP iH
my_list = [1,2,3,4,5]
print(my_list[::-1])
# [5, 4, 3, 2, 1]

python复制代码word_list = ["awesome", "is", "this"]
print(' '.join(word_list[::-1]) + '!')
#this is awesome!

python复制代码def stupid_func(x):
    return x**2 + 5

python复制代码def stupid_func(x):
    return x**2 + 5

my_list = [1, 2, 3, 4, 5]
new_list = []
for x in my_list:
     if x % 2 != 0:
         new_list.append(stupid_func(x))
print(new_list)
#[6, 14, 30]

python复制代码def stupid_func(x):
    return x**2 + 5

my_list = [1, 2, 3, 4, 5]
print([stupid_func(x) for x in my_list if x % 2 != 0])
#[6, 14, 30]

python复制代码for item in list:
     if conditional:
         expression

python复制代码my_list = [1, 2, 3, 4, 5]

print([x ** 2 + 5 for x in my_list if x % 2 != 0])
#[6, 14, 30]

python复制代码stupid_func = (lambda x : x ** 2 + 5)
print([stupid_func(1), stupid_func(3), stupid_func(5)])
#[6, 14, 30]

python复制代码my_list = [2, 1, 0, -1, -2]
print(sorted(my_list))
#[-2, -1, 0, 1, 2]

python复制代码my_list = [2, 1, 0, -1, -2]
print(sorted(my_list, key = lambda x : x ** 2))
#[0, -1, 1, -2, 2]

python复制代码print(list(map(lambda x, y : x * y, [1, 2, 3], [4, 5, 6])))
#[4, 10, 18]

python复制代码x, y = [1, 2, 3], [4, 5, 6]
z = []
for i in range(len(x)):
    z.append(x[i] * y[i])
print(z)
#[4, 10, 18]

python复制代码x = int(input())
if x >= 10:
    print("Horse")
elif 1 < x < 10:
    print("Duck")
else:
    print("Baguette")

bash复制代码print("Horse" if x >= 10 else "Duck" if 1 < x < 10 else "Baguette")

python复制代码first_names = ["Peter", "Christian", "Klaus"]
last_names = ["Jensen", "Smith", "Nistrup"]
print([' '.join(x) for x in zip(first_names, last_names)])
#['Peter Jensen', 'Christian Smith', 'Klaus Nistrup']

复制代码sudo yum install libcurl openssl

arduino复制代码sudo apt-get install libcurl4 openssl

arduino复制代码sudo apt-get install libcurl3 openssl

css复制代码lsb_release -a

bash复制代码wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-4.4.10.tgz #下载
wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-4.4.10.tgz #解压

bash复制代码export PATH=<mongodb-install-directory>/bin:$PATH

bash复制代码sudo mkdir -p /var/lib/mongo
sudo mkdir -p /var/log/mongodb

css复制代码mongod --dbpath /var/lib/mongo --logpath /var/log/mongodb/mongod.log --fork

sql复制代码toby@recsys:~$ mongo
MongoDB shell version: 2.6.10
connecting to: test
> show dbs
admin  (empty)
local  0.078GB

css复制代码toby@recsys:~$ mongo
MongoDB shell version: 2.6.10
connecting to: test
> db
test

css复制代码toby@recsys:~$ mongo
MongoDB shell version: 2.6.10
connecting to: test
> use admin
switched to db admin
> db
admin
>

perl复制代码use DATABASE_NAME

css复制代码toby@recsys:~$ mongo
MongoDB shell version: 2.6.10
connecting to: test
> use tobytest
switched to db tobytest
> db
tobytest
>

sql复制代码> show dbs
admin  (empty)
local  0.078GB
>

sql复制代码> db.tobytest.insert({"name":"Toby"})
WriteResult({ "nInserted" : 1 })
> show dbs
admin     (empty)
local     0.078GB
tobytest  0.078GB
>

scss复制代码db.createCollection(name, options)

javascript复制代码> use tobytest
switched to db tobytest
> db.createCollection("tobycollection")
{ "ok" : 1 }
>

markdown复制代码> show tables
system.indexes
tobycollection
tobytest
>

scss复制代码db.collection.drop()

markdown复制代码> use tobytest
switched to db tobytest
> show collections
system.indexes
tobycollection
tobytest
>

markdown复制代码> db.tobycollection.drop()
true
>

markdown复制代码> show collections
system.indexes
tobytest
>

javascript复制代码db.COLLECTION_NAME.insert(document)
或
db.COLLECTION_NAME.save(document)

php复制代码> db.col.insert({title:'Toby MongoDB',
... description:'this is MongoDB',
... tags:['mongodb','database','NoSQL'],
... likes:1
... })
WriteResult({ "nInserted" : 1 })
>

javascript复制代码> db.col.find()
{ "_id" : ObjectId("617970fc286e9ff2b1250d70"), "title" : "Toby MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
>

python复制代码> document=({title:'Toby another MongoDB',
... description:'this is another MongoDB',
... tags:['mongodb','database','NoSQL'],
... likes:2
... })

json复制代码{
	"title" : "Toby another MongoDB",
	"description" : "this is another MongoDB",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 2
}

javascript复制代码> db.col.insert(document)
WriteResult({ "nInserted" : 1 })
> db.col.find()
{ "_id" : ObjectId("617970fc286e9ff2b1250d70"), "title" : "Toby MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
{ "_id" : ObjectId("61797229286e9ff2b1250d71"), "title" : "Toby another MongoDB", "description" : "this is another MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 2 }
>

php复制代码db.collection.update(
   <query>,
   <update>,
   {
     upsert: <boolean>,
     multi: <boolean>,
     writeConcern: <document>
   }
)

php复制代码> db.col.insert({title:'Toby MongoDB',
... description:'this is MongoDB',
... tags:['mongodb','database','NoSQL'],
... likes:1
... })
WriteResult({ "nInserted" : 1 })
>

css复制代码> db.col.update({'title':'Toby MongoDB'},{$set:{'title':'MongoDB'}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.col.find().pretty()
{
	"_id" : ObjectId("617970fc286e9ff2b1250d70"),
	"title" : "MongoDB",
	"description" : "this is MongoDB",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 1
}
{
	"_id" : ObjectId("61797229286e9ff2b1250d71"),
	"title" : "Toby another MongoDB",
	"description" : "this is another MongoDB",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 2
}
>

xml复制代码db.collection.remove(
   <query>,
   <justOne>
)

php复制代码db.collection.remove(
   <query>,
   {
     justOne: <boolean>,
     writeConcern: <document>
   }
)

php复制代码> db.col.insert({title:'Toby MongoDB', description:'this is MongoDB', tags:['mongodb','database','NoSQL'], likes:1 })
WriteResult({ "nInserted" : 1 })
> db.col.insert({title:'Toby MongoDB', description:'this is MongoDB', tags:['mongodb','database','NoSQL'], likes:1 })
WriteResult({ "nInserted" : 1 })
>

css复制代码> db.col.find()
{ "_id" : ObjectId("617970fc286e9ff2b1250d70"), "title" : "MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
{ "_id" : ObjectId("61797229286e9ff2b1250d71"), "title" : "Toby another MongoDB", "description" : "this is another MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 2 }
{ "_id" : ObjectId("6179747d286e9ff2b1250d72"), "title" : "Toby MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
{ "_id" : ObjectId("61797481286e9ff2b1250d73"), "title" : "Toby MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
>

csharp复制代码> db.col.remove({'title':'Toby MongoDB'})
WriteResult({ "nRemoved" : 2 }) # 删除了两个
> db.col.find()
{ "_id" : ObjectId("617970fc286e9ff2b1250d70"), "title" : "MongoDB", "description" : "this is MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 1 }
{ "_id" : ObjectId("61797229286e9ff2b1250d71"), "title" : "Toby another MongoDB", "description" : "this is another MongoDB", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 2 }
>

csharp复制代码>db.COLLECTION_NAME.remove(DELETION_CRITERIA,1)

scss复制代码> db.col.remove({})
WriteResult({ "nRemoved" : 2 })
> db.col.find()
>

lua复制代码db.collection.find(query, projection)

scss复制代码>db.col.find().pretty()

php复制代码> db.col.insert({title:'Toby MongoDB', description:'this is MongoDB',by:'Toby', tags:['mongodb','database','NoSQL'], likes:100 })
WriteResult({ "nInserted" : 1 })
> db.col.find().pretty()
{
	"_id" : ObjectId("6179772f286e9ff2b1250d75"),
	"title" : "Toby MongoDB",
	"description" : "this is MongoDB",
	"by" : "Toby",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 100
}
>

php复制代码>db.col.find({key1:value1, key2:value2}).pretty()

javascript复制代码> db.col.find({'by':'Toby','title':'Toby MongoDB'}).prettydb.col.find({'by':'Toby','title':'Toby MongoDB'}).pretty()
{
	"_id" : ObjectId("6179772f286e9ff2b1250d75"),
	"title" : "Toby MongoDB",
	"description" : "this is MongoDB",
	"by" : "Toby",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 100
}
>

css复制代码>db.col.find(
   {
      $or: [
         {key1: value1}, {key2:value2}
      ]
   }
).pretty()

css复制代码> db.col.find({$or:[{"by":"Toby"},{"title":"Toby MongoDB"}]}).pretty()
{
	"_id" : ObjectId("6179772f286e9ff2b1250d75"),
	"title" : "Toby MongoDB",
	"description" : "this is MongoDB",
	"by" : "Toby",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 100
}
>

css复制代码> db.col.find({"likes":{$gt:50},$or:[{"by":"Toby"},{"title":"Toby MongoDB"}]}).pretty()
{
	"_id" : ObjectId("6179772f286e9ff2b1250d75"),
	"title" : "Toby MongoDB",
	"description" : "this is MongoDB",
	"by" : "Toby",
	"tags" : [
		"mongodb",
		"database",
		"NoSQL"
	],
	"likes" : 100
}
>

lua复制代码>db.COLLECTION_NAME.find().sort({KEY:1})

css复制代码> db.col.find().pretty()
{
	"_id" : ObjectId("61797a56286e9ff2b1250d78"),
	"title" : "Toby PHP",
	"description" : "this is PHP",
	"by" : "Toby",
	"tags" : [
		"PHP",
		"Language"
	],
	"likes" : 100
}
{
	"_id" : ObjectId("61797a62286e9ff2b1250d79"),
	"title" : "Toby JAVA",
	"description" : "this is JAVA",
	"by" : "Toby",
	"tags" : [
		"JAVA",
		"Language"
	],
	"likes" : 50
}
{
	"_id" : ObjectId("61797a83286e9ff2b1250d7a"),
	"title" : "Toby Python",
	"description" : "this is Python",
	"by" : "Toby",
	"tags" : [
		"Python",
		"Language"
	],
	"likes" : 20
}
>

javascript复制代码> db.col.find({},{'title':1,_id:0}).sort({"likes":-1})
{ "title" : "Toby PHP" }
{ "title" : "Toby JAVA" }
{ "title" : "Toby Python" }
>

ruby复制代码$ python3 -m pip install pymongo

arduino复制代码import pymongo

python复制代码import pymongo
myclient=pymongo.MongoClient("mongodb://localhost:27017/")
mydb=myclient["pydb"]

python复制代码import pymongo
myclient=pymongo.MongoClient("mongodb://localhost:27017/")
mydb=myclient["pydb"]

dblist = myclient.list_database_names()
# dblist = myclient.database_names() 
if "pydb" in dblist:
  print("数据库已存在！")
else:
  print('数据库不存在')

python复制代码import pymongo
myclient=pymongo.MongoClient("mongodb://localhost:27017/")
mydb=myclient["pydb"]

mycol=myclient["col_set"]

python复制代码import pymongo
myclient=pymongo.MongoClient("mongodb://localhost:27017/")
mydb=myclient["pydb"]

mycol=myclient["col_set"]

collist = mydb. list_collection_names()
if "col_set" in collist:   # 判断 sites 集合是否存在
  print("集合已存在！")
else:
  print('集合不存在')

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
 
mydict = { "name": "Toby", "age": "23", "url": "https://juejin.cn/user/3403743731649863" }
 
x = mycol.insert_one(mydict) 
print(x)

css复制代码> use pydb
switched to db pydb
> db.col_set.find()
{ "_id" : ObjectId("617ce42cbc6011eaf1529012"), "name" : "Toby", "url" : "https://juejin.cn/user/3403743731649863", "age" : "23" }
>

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
 
mylist = [
  { "name": "Tom", "age": "100", "url": "https://juejin.cn/user/3403743731649863" },
  { "name": "Mary", "age": "101", "url": "https://juejin.cn/user/3403743731649863" },
  { "name": "Timi", "age": "10", "url": "https://juejin.cn/user/3403743731649863" },
]
 
x = mycol.insert_many(mylist)
 
# 输出插入的所有文档对应的 _id 值
print(x.inserted_ids)

css复制代码> use pydb
switched to db pydb
> db.col_set.find()
{ "_id" : ObjectId("617ce42cbc6011eaf1529012"), "name" : "Toby", "url" : "https://juejin.cn/user/3403743731649863", "age" : "23" }
{ "_id" : ObjectId("617ce591826d13d898f97890"), "name" : "Tom", "url" : "https://juejin.cn/user/3403743731649863", "age" : "100" }
{ "_id" : ObjectId("617ce591826d13d898f97891"), "name" : "Mary", "url" : "https://juejin.cn/user/3403743731649863", "age" : "101" }
{ "_id" : ObjectId("617ce591826d13d898f97892"), "name" : "Timi", "url" : "https://juejin.cn/user/3403743731649863", "age" : "10" }
>

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
 
x = mycol.find_one()
 
print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
for x in mycol.find():
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
for x in mycol.find({},{ "_id": 0, "name": 1, "age": 1 }):
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
myquery = { "name": "Toby" }
 
mydoc = mycol.find(myquery)
 
for x in mydoc:
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
myresult = mycol.find().limit(3)
 
# 输出结果
for x in myresult:
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
myquery = { "age": "23" }
newvalues = { "$set": { "age": "12345" } }
 
mycol.update_one(myquery, newvalues)
 
# 输出修改后的  "sites"  集合
for x in mycol.find():
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
mydoc = mycol.find().sort("age")
for x in mydoc:
  print(x)

python复制代码import pymongo
 
myclient = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = myclient["pydb"]
mycol = mydb["col_set"]
  
mydoc = mycol.find().sort("alexa", -1)
 
for x in mydoc:
  print(x)