复制代码public class test {
    private int f() {
        f();
    }
    public static void main(String[] args) {
        f();
    }
}

复制代码public void test() {
    String name = "stormma";
    int age = 21;
}
JAVA架构群：678779467

复制代码public void test() {
    Object obj = new Object();
}
JAVA架构群：678779467

复制代码codeArea = new CodeArea();
        codeArea.setParagraphGraphicFactory(LineNumberFactory.get(codeArea));
        codeArea.richChanges()
                .filter(ch -> !ch.getInserted().equals(ch.getRemoved())) // XXX
                .successionEnds(Duration.ofMillis(500))
                .supplyTask(this::computeHighlightingAsync)
                .awaitLatest(codeArea.richChanges())
                .filterMap(t -> {
                    if(t.isSuccess()) {
                        return Optional.of(t.get());
                    } else {
                        t.getFailure().printStackTrace();
                        return Optional.empty();
                    }
                })
                .subscribe(this::applyHighlighting);
        codeArea.replaceText(0, 0, HostsUtil.getHostsContent());

复制代码private static final String KEYWORD_PATTERN = "([1-9]|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5])(\\.(\\d|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5])){3}\\b";
    private static final String COMMENT_PATTERN = "#[^\n]*";
 
    private static final Pattern PATTERN = Pattern.compile(
        "(?<KEYWORD>" + KEYWORD_PATTERN + ")"
        + "|(?<COMMENT>" + COMMENT_PATTERN + ")"
    );
 
private static StyleSpans<Collection<String>> computeHighlighting(String text) {
        Matcher matcher = PATTERN.matcher(text);
        int lastKwEnd = 0;
        StyleSpansBuilder<Collection<String>> spansBuilder
                = new StyleSpansBuilder<>();
        while(matcher.find()) {
            String styleClass =
                    matcher.group("KEYWORD") != null ? "keyword" :
                    matcher.group("COMMENT") != null ? "comment" :
                    null; /* never happens */ assert styleClass != null;
            spansBuilder.add(Collections.emptyList(), matcher.start() - lastKwEnd);
            spansBuilder.add(Collections.singleton(styleClass), matcher.end() - matcher.start());
            lastKwEnd = matcher.end();
        }
        spansBuilder.add(Collections.emptyList(), text.length() - lastKwEnd);
        return spansBuilder.create();
    }

复制代码private Task<StyleSpans<Collection<String>>> computeHighlightingAsync() {
        String text = codeArea.getText();
        Task<StyleSpans<Collection<String>>> task = new Task<StyleSpans<Collection<String>>>() {
            @Override
            protected StyleSpans<Collection<String>> call() throws Exception {
                return computeHighlighting(text);
            }
        };
        executor.execute(task);
        return task;
    }
 
    private void applyHighlighting(StyleSpans<Collection<String>> highlighting) {
        codeArea.setStyleSpans(0, highlighting);
    }

复制代码Scene scene = new Scene(new StackPane(new VirtualizedScrollPane<>(codeArea)), 600, 400);
        scene.getStylesheets().add(HostsEditor.class.getResource("hosts-keywords.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.setTitle("JHosts Manager");
        primaryStage.show();

复制代码codeArea.setOnKeyPressed(new EventHandler<KeyEvent>()
        {
            @Override
            public void handle(KeyEvent event)
            {
                if (keyCombinationCtrlS.match(event))
                {
                    Boolean ret = HostsUtil.saveHostsContent(codeArea.getText());
                    if(ret == true){
                        System.out.println("save success!");
                        codeArea.setStyle("-fx-border-color: green;");
                    } else {
                        System.out.println("save error!");
                        codeArea.setStyle("-fx-border-color: red;");
                    }
                }
            }
        });

复制代码if(SystemUtils.IS_OS_MAC){
            primaryStage.getIcons().addAll(new Image("file:icon.icns"));
        } else {
            primaryStage.getIcons().addAll(new Image("file:icon.png"));
        }

复制代码/**
 * Transfers all entries from current table to newTable.
 */
void transfer(Entry[] newTable, boolean rehash) {
    int newCapacity = newTable.length;
    for (Entry<K,V> e : table) {
        while(null != e) {
            Entry<K,V> next = e.next;
            if (rehash) {
                e.hash = null == e.key ? 0 : hash(e.key);
            }
            int i = indexFor(e.hash, newCapacity);
            e.next = newTable[i];
            newTable[i] = e;
            e = next;
        }
    }
}

复制代码pip install scrapy

复制代码python scripts.py

复制代码scrapy crawl <项目名>

复制代码public class HashMap<K,V>
    extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable

复制代码 /**
     * The default initial capacity - MUST be a power of two.
     * 默认初始容量-必须是2的幂。
     */
    static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

复制代码/**
     * The maximum capacity, used if a higher value is implicitly specified
     * by either of the constructors with arguments.
     * MUST be a power of two <= 1<<30.
     *如果有一个更大的值被用于构造HashMap,则使用最大值
     */
    static final int MAXIMUM_CAPACITY = 1 << 30;

复制代码/**
     * The load factor used when none specified in constructor.
     * 加载因子，如果构造函数中没有指定，则使用默认的
     */
    static final float DEFAULT_LOAD_FACTOR = 0.75f;

复制代码/**
     * An empty table instance to share when the table is not inflated.
     * 当表不膨胀时共享的空表实例。
     */
    static final Entry<?,?>[] EMPTY_TABLE = {};

复制代码/**
     * The table, resized as necessary. Length MUST Always be a power of two.
     */
    transient Entry<K,V>[] table = (Entry<K,V>[]) EMPTY_TABLE;

复制代码/**
     * The number of key-value mappings contained in this map.
     */
    transient int size;

复制代码/**
     * The next size value at which to resize (capacity * load factor).
     * @serial
     */
    // If table == EMPTY_TABLE then this is the initial capacity at which the
    // table will be created when inflated.
    int threshold;

复制代码    /**
     * The load factor for the hash table.
     *
     * @serial
     */
    final float loadFactor;

复制代码/**
     * The number of times this HashMap has been structurally modified
     * Structural modifications are those that change the number of mappings in
     * the HashMap or otherwise modify its internal structure (e.g.,
     * rehash).  This field is used to make iterators on Collection-views of
     * the HashMap fail-fast.  (See ConcurrentModificationException).
     */
    transient int modCount;

复制代码/**
     * A randomizing value associated with this instance that is applied to
     * hash code of keys to make hash collisions harder to find. If 0 then
     * alternative hashing is disabled.
     */
    transient int hashSeed = 0;

复制代码static class Entry<K,V> implements Map.Entry<K,V>

复制代码static class Entry<K,V> implements Map.Entry<K,V> {
        final K key; //键对象
        V value;     //值对象
        Entry<K,V> next; //指向链表中下一个Entry对象，可为null，表示当前Entry对象在链表尾部
        int hash;    //键对象的hash值

        /**
         * 构造对象
         */
        Entry(int h, K k, V v, Entry<K,V> n) {
            value = v;
            next = n;
            key = k;
            hash = h;
        }
        /**
        * 获取key
        */
        public final K getKey() {
            return key;
        }
        /**
        * 获取value
        */
        public final V getValue() {
            return value;
        }
        /**
        * 设置value，这里返回的是oldValue(这个不太明白，哪位大佬清楚的可以留言解释下，非常感谢)
        */
        public final V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }
        /**
        * 重写equals方法
        */
        public final boolean equals(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            Object k1 = getKey();
            Object k2 = e.getKey();
            if (k1 == k2 || (k1 != null && k1.equals(k2))) {
                Object v1 = getValue();
                Object v2 = e.getValue();
                if (v1 == v2 || (v1 != null && v1.equals(v2)))
                    return true;
            }
            return false;
        }
        /**
        * 重写hashCode方法
        */
        public final int hashCode() {
            return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue());
        }

        public final String toString() {
            return getKey() + "=" + getValue();
        }

        /**
         * This method is invoked whenever the value in an entry is
         * overwritten by an invocation of put(k,v) for a key k that's already
         * in the HashMap.
         */
        void recordAccess(HashMap<K,V> m) {
        }

        /**
         * This method is invoked whenever the entry is
         * removed from the table.
         */
        void recordRemoval(HashMap<K,V> m) {
        }
    }

复制代码public static void main(String[] args) throws Exception {
		HashMap<String, Object> map=new HashMap<>();
		for (int i = 0; i < 170; i++) {
			map.put("key"+i, i);
		}
		System.out.println(map);
	}

复制代码 /**
     * Constructs an empty <tt>HashMap</tt> with the specified initial
     * capacity and load factor.
     *
     * @param  initialCapacity the initial capacity 指定的初始化容量大小
     * @param  loadFactor      the load factor 指定的负载因子
     * @throws IllegalArgumentException if the initial capacity is negative
     *         or the load factor is nonpositive
     */
    public HashMap(int initialCapacity, float loadFactor) {
        //如果初始化容量小于0，则抛出异常
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal initial capacity: " +
                                               initialCapacity);
        //如果初始化容量大于最大容量，则使用默认最大容量
        if (initialCapacity > MAXIMUM_CAPACITY)
            initialCapacity = MAXIMUM_CAPACITY;
       //如果负载因子小于0或者非数值类型，则抛出异常
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new IllegalArgumentException("Illegal load factor: " +
                                               loadFactor);
        //初始化负载因子
        this.loadFactor = loadFactor;
        //初始化threshold
        threshold = initialCapacity;
        //这个初始化方法是个空方法，应该是意在HashMap的子类中由使用者自行重写该方法的具体实现
        init();
    }

复制代码//只制定默认容量
 public HashMap(int initialCapacity) {
        this(initialCapacity, DEFAULT_LOAD_FACTOR);
 }
 //使用HashMap默认的容量大小和负载因子
 public HashMap() {
        this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
 }

复制代码public HashMap(Map<? extends K, ? extends V> m) {
        this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
                      DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
        inflateTable(threshold);

        putAllForCreate(m);
    }

复制代码public V put(K key, V value) {
        //如果table是空的
        if (table == EMPTY_TABLE) {
            //inflate：扩容/膨胀的意思
            inflateTable(threshold);
        }
        //如果key为null 此处敲下桌子，为什么可以存null？
        if (key == null)
            //执行putForNullKey方法，这个方法的作用是如果key为null，就将当前的k-v存放到table[0],即第一个桶。
            return putForNullKey(value);
        //对key进行一次hash运算，获取hash值
        int hash = hash(key);
        //根据key值得hash值和表的长度来计算索引位置
        int i = indexFor(hash, table.length);
        //移动数据，插入数据
        for (Entry<K,V> e = table[i]; e != null; e = e.next) {
            Object k;
            if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
                V oldValue = e.value;
                e.value = value;
                e.recordAccess(this);
                //上面Entry中的setValue中也有提到，返回的都是旧的数据
                return oldValue;
            }
        }

        modCount++;
        addEntry(hash, key, value, i);
        return null;
    }

复制代码/**
    final int hash(Object k) {
        int h = hashSeed;
        if (0 != h && k instanceof String) {
            return sun.misc.Hashing.stringHash32((String) k);
        }

        h ^= k.hashCode();

        //这个函数确保在每个比特位置上仅以恒定倍数不同
        //的散列码具有有限数量的冲突（在默认加载因子下大约为8）。
        h ^= (h >>> 20) ^ (h >>> 12);
        return h ^ (h >>> 7) ^ (h >>> 4);
    }

复制代码 public V get(Object key) {
        //和存null key一样，取的时候也是从table[0]取
        if (key == null)
            return getForNullKey();
        //获取entry
        Entry<K,V> entry = getEntry(key);

        return null == entry ? null : entry.getValue();
    }

复制代码 final Entry<K,V> getEntry(Object key) {
        //size等于0，说明当前hashMap中没有元素，直接返回null（每个entry默认值为null）
        if (size == 0) {
            return null;
        }
        //根据key值计算hash值
        int hash = (key == null) ? 0 : hash(key);
        //通过hash值获取到索引位置，找到对应的桶链进行遍历查找
        for (Entry<K,V> e = table[indexFor(hash, table.length)];
             e != null;
             e = e.next) {
            Object k;
            //如果找到则返回，如果没有链表指针移动到下一个节点继续查找。
            if (e.hash == hash &&
                ((k = e.key) == key || (key != null && key.equals(k))))
                return e;
        }
        return null;
    }

复制代码void addEntry(int hash, K key, V value, int bucketIndex) {
        //如果当前size超过threshold 并且满足桶索引位置不为null的情况下，扩容
        if ((size >= threshold) && (null != table[bucketIndex])) {
           //扩容之后为原来的两倍
            resize(2 * table.length);
            //重新计算hash值
            hash = (null != key) ? hash(key) : 0;
            //重写计算索引
            bucketIndex = indexFor(hash, table.length);
        }
        //执行具体的插入操作
        createEntry(hash, key, value, bucketIndex);
    }

void createEntry(int hash, K key, V value, int bucketIndex) {
        //先取到当前桶的entry
        Entry<K,V> e = table[bucketIndex];
        //将新的数据插入到table[bucketIndex]，再将之前的entry通过链表简介到table[bucketIndex]的next指向；前面的图已经进行了描述。
        table[bucketIndex] = new Entry<>(hash, key, value, e);
        size++;
    }

复制代码<html>
<body>
<h1 th:text="#{label.form.title}">form</h1>
<form action="/" th:object="${user}" method="POST" enctype="utf8">
    <div>
        <label th:text="#{label.user.firstName}">first</label>
        <input th:field="*{firstName}"/>
        <p th:each="error: ${fields.errors('firstName')}"
          th:text="${error}">Validation error</p>
    </div>
    <div>
        <label th:text="#{label.user.lastName}">last</label>
        <input th:field="*{lastName}"/>
        <p th:each="error : ${fields.errors('lastName')}"
          th:text="${error}">Validation error</p>
    </div>
    <div>
        <label th:text="#{label.user.email}">email</label>
        <input type="email" th:field="*{email}"/>
        <p th:each="error : ${fields.errors('email')}"
          th:text="${error}">Validation error</p>
    </div>
    <div>
        <label th:text="#{label.user.password}">password</label>
        <input type="password" th:field="*{password}"/>
        <p th:each="error : ${fields.errors('password')}"
          th:text="${error}">Validation error</p>
    </div>
    <div>
        <label th:text="#{label.user.confirmPass}">confirm</label>
        <input type="password" th:field="*{matchingPassword}"/>
    </div>
    <button type="submit" th:text="#{label.form.submit}">submit</button>
</form>
 
<a th:href="@{/login.html}" th:text="#{label.form.loginLink}">login</a>
</body>
</html>

复制代码public class UserDto {
    @NotNull
    @NotEmpty
    private String firstName;
     
    @NotNull
    @NotEmpty
    private String lastName;
     
    @NotNull
    @NotEmpty
    private String password;
    private String matchingPassword;
     
    @NotNull
    @NotEmpty
    private String email;
     
    // standard getters and setters
}

复制代码@RequestMapping(value = "/user/registration", method = RequestMethod.GET)
public String showRegistrationForm(WebRequest request, Model model) {
    UserDto userDto = new UserDto();
    model.addAttribute("user", userDto);
    return "registration";
}

复制代码public ModelAndView registerUserAccount(
  @ModelAttribute("user") @Valid UserDto accountDto, 
  BindingResult result, WebRequest request, Errors errors) {
    ...
}

复制代码@Target({TYPE, FIELD, ANNOTATION_TYPE}) 
@Retention(RUNTIME)
@Constraint(validatedBy = EmailValidator.class)
@Documented
public @interface ValidEmail {   
    String message() default "Invalid email";
    Class<?>[] groups() default {}; 
    Class<? extends Payload>[] payload() default {};
}

复制代码public class EmailValidator 
  implements ConstraintValidator<ValidEmail, String> {
     
    private Pattern pattern;
    private Matcher matcher;
    private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-+]+
        (.[_A-Za-z0-9-]+)*@" + "[A-Za-z0-9-]+(.[A-Za-z0-9]+)*
        (.[A-Za-z]{2,})$"; 
    @Override
    public void initialize(ValidEmail constraintAnnotation) {       
    }
    @Override
    public boolean isValid(String email, ConstraintValidatorContext context){   
        return (validateEmail(email));
    } 
    private boolean validateEmail(String email) {
        pattern = Pattern.compile(EMAIL_PATTERN);
        matcher = pattern.matcher(email);
        return matcher.matches();
    }
}

复制代码@ValidEmail
@NotNull
@NotEmpty
private String email;

复制代码@Target({TYPE,ANNOTATION_TYPE}) 
@Retention(RUNTIME)
@Constraint(validatedBy = PasswordMatchesValidator.class)
@Documented
public @interface PasswordMatches { 
    String message() default "Passwords don't match";
    Class<?>[] groups() default {}; 
    Class<? extends Payload>[] payload() default {};
}

复制代码public class PasswordMatchesValidator 
  implements ConstraintValidator<PasswordMatches, Object> { 
     
    @Override
    public void initialize(PasswordMatches constraintAnnotation) {       
    }
    @Override
    public boolean isValid(Object obj, ConstraintValidatorContext context){   
        UserDto user = (UserDto) obj;
        return user.getPassword().equals(user.getMatchingPassword());    
    }     
}

复制代码@PasswordMatches
public class UserDto {
   ...
}

复制代码@RequestMapping(value = "/user/registration", method = RequestMethod.POST)
public ModelAndView registerUserAccount
      (@ModelAttribute("user") @Valid UserDto accountDto, 
      BindingResult result, WebRequest request, Errors errors) {    
    User registered = new User();
    if (!result.hasErrors()) {
        registered = createUserAccount(accountDto, result);
    }
    if (registered == null) {
        result.rejectValue("email", "message.regError");
    }
    // rest of the implementation
}
private User createUserAccount(UserDto accountDto, BindingResult result) {
    User registered = null;
    try {
        registered = service.registerNewUserAccount(accountDto);
    } catch (EmailExistsException e) {
        return null;
    }    
    return registered;
}

复制代码@Service
public class UserService implements IUserService {
    @Autowired
    private UserRepository repository; 
     
    @Transactional
    @Override
    public User registerNewUserAccount(UserDto accountDto) 
      throws EmailExistsException {
         
        if (emailExist(accountDto.getEmail())) {  
            throw new EmailExistsException(
              "There is an account with that email adress: "
              +  accountDto.getEmail());
        }
        ...
        // 其余的注册操作逻辑
    }
    private boolean emailExist(String email) {
        User user = repository.findByEmail(email);
        if (user != null) {
            return true;
        }
        return false;
    }
}

复制代码@RequestMapping(value = "/user/registration", method = RequestMethod.POST)
public ModelAndView registerUserAccount(
  @ModelAttribute("user") @Valid UserDto accountDto, 
  BindingResult result, 
  WebRequest request, 
  Errors errors) {
     
    User registered = new User();
    if (!result.hasErrors()) {
        registered = createUserAccount(accountDto, result);
    }
    if (registered == null) {
        result.rejectValue("email", "message.regError");
    }
    if (result.hasErrors()) {
        return new ModelAndView("registration", "user", accountDto);
    } 
    else {
        return new ModelAndView("successRegister", "user", accountDto);
    }
}
private User createUserAccount(UserDto accountDto, BindingResult result) {
    User registered = null;
    try {
        registered = service.registerNewUserAccount(accountDto);
    } catch (EmailExistsException e) {
        return null;
    }
    return registered;
}

复制代码public interface IUserService {
    User registerNewUserAccount(UserDto accountDto)     
      throws EmailExistsException;
}

复制代码@Service
public class UserService implements IUserService {
    @Autowired
    private UserRepository repository;
     
    @Transactional
    @Override
    public User registerNewUserAccount(UserDto accountDto) 
      throws EmailExistsException {
         
        if (emailExist(accountDto.getEmail())) {   
            throw new EmailExistsException(
              "There is an account with that email address:  + accountDto.getEmail());
        }
        User user = new User();    
        user.setFirstName(accountDto.getFirstName());
        user.setLastName(accountDto.getLastName());
        user.setPassword(accountDto.getPassword());
        user.setEmail(accountDto.getEmail());
        user.setRoles(Arrays.asList("ROLE_USER"));
        return repository.save(user);       
    }
    private boolean emailExist(String email) {
        User user = repository.findByEmail(email);
        if (user != null) {
            return true;
        }
        return false;
    }
}

复制代码@Service
@Transactional
public class MyUserDetailsService implements UserDetailsService {
  
    @Autowired
    private UserRepository userRepository;
    // 
    public UserDetails loadUserByUsername(String email)
      throws UsernameNotFoundException {
  
        User user = userRepository.findByEmail(email);
        if (user == null) {
            throw new UsernameNotFoundException(
              "No user found with username: "+ email);
        }
        boolean enabled = true;
        boolean accountNonExpired = true;
        boolean credentialsNonExpired = true;
        boolean accountNonLocked = true;
        return  new org.springframework.security.core.userdetails.User
          (user.getEmail(), 
          user.getPassword().toLowerCase(), enabled, accountNonExpired, 
          credentialsNonExpired, accountNonLocked, 
          getAuthorities(user.getRoles()));
    }
     
    private static List<GrantedAuthority> getAuthorities (List<String> roles) {
        List<GrantedAuthority> authorities = new ArrayList<>();
        for (String role : roles) {
            authorities.add(new SimpleGrantedAuthority(role));
        }
        return authorities;
    }
}

复制代码<authentication-manager>
    <authentication-provider user-service-ref="userDetailsService" /> 
</authentication-manager>
  
<beans:bean id="userDetailsService"
  class="org.baeldung.security.MyUserDetailsService"/>

复制代码@Autowired
private MyUserDetailsService userDetailsService;
 
@Override
protected void configure(AuthenticationManagerBuilder auth) 
  throws Exception {
    auth.userDetailsService(userDetailsService);
}

复制代码boolean add(E e);

复制代码public class Test1 {
    public static void main(String[] args) {
        List a = new ArrayList();
        a.add("123");
        a.add(1);             
        // 以上代码可以正常通过编译，其中同时含有了Integer类型和String类型
        for (int i = 0 ; i < a.size(); i++) {
            int result = (Integer)a.get(i);    // 在取出时需要对Object进行强制转型
            System.out.println(result);
        }
    }
}

复制代码public class Test1 {
    public static void main(String[] args) {
        List<Integer> a = new ArrayList();
        a.add("123");          // 编译不通过
        a.add(1);
    }
}

复制代码public class Test1 {
    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        List<Integer> a = new ArrayList();
        List b = new ArrayList();
        a.getClass().getMethod("add",Object.class).invoke(a,"abc");    
        // 以上代码编译通过，运行通过
    }
}

复制代码class Pair<T> {
    private T value;
    public T getValue() {
        return value;
    }
    public void setValue(T  value) {
        this.value = value;
    }
} 
  
Pair<T>的原始类型为：
class Pair {
    private Object value;
    public Object getValue() {
        return value;
    }
    public void setValue(Object  value) {
        this.value = value;
    }
}

复制代码public class Test1 {
 
   public static void main(String[] args) {
 
      /** 不指定泛型的时候 */
      int i = Test1.add(1, 2); // 这两个参数都是Integer，所以T为Integer类型
      Number f = Test1.add(1, 1.2);// 这两个参数一个是Integer，以风格是Float，所以取同一父类的最小级，为Number
      Object o = Test1.add(1, "asd");// 这两个参数一个是Integer，以风格是Float，所以取同一父类的最小级，为Object
 
      /** 指定泛型的时候 */
      int a = Test1.<Integer> add(1, 2);// 指定了Integer，所以只能为Integer类型或者其子类
      int b = Test1.<Integer> add(1, 2.2);// 编译错误，指定了Integer，不能为Float
      Number c = Test1.<Number> add(1, 2.2); // 指定为Number，所以可以为Integer和Float
   }
 
   // 这是一个简单的泛型方法
   public static <T> T add(T x, T y) {
      return y;
   }
}

复制代码public class Test1 {
 
    public static void main(String[] args) {
        List<Integer> a = new ArrayList();
        a.add(1);
 
        for (int i = 0 ; i < a.size(); i++) {
            int result = a.get(i);
            System.out.println(result);
        }
    }
}

复制代码public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class java/util/ArrayList
       3: dup
       4: invokespecial #3                  // Method java/util/ArrayList."<init>":()V
       7: astore_1
       8: aload_1
       9: iconst_1
      10: invokestatic  #4                  // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
      13: invokeinterface #5,  2            // InterfaceMethod java/util/List.add:(Ljava/lang/Object;)Z
      18: pop
      19: iconst_0
      20: istore_2
      21: iload_2
      22: aload_1
      23: invokeinterface #6,  1            // InterfaceMethod java/util/List.size:()I
      28: if_icmpge     58
      31: aload_1
      32: iload_2
      33: invokeinterface #7,  2            // InterfaceMethod java/util/List.get:(I)Ljava/lang/Object;
      38: checkcast     #8                  // class java/lang/Integer       这里JVM做了强转
      41: invokevirtual #9                  // Method java/lang/Integer.intValue:()I
      44: istore_3
      45: getstatic     #10                 // Field java/lang/System.out:Ljava/io/PrintStream;
      48: iload_3
      49: invokevirtual #11                 // Method java/io/PrintStream.println:(I)V
      52: iinc          2, 1
      55: goto          21
      58: return

复制代码public class Test1 {
 
   public static void main(String[] args) {
      DateInter dateInter = new DateInter();
      dateInter.setValue(new Date());
      dateInter.setValue(new Object());// 编译错误
   }
}
 
class Pair<T> {
   private T value;
 
   public T getValue() {
      return value;
   }
 
   public void setValue(T value) {
      this.value = value;
   }
}
 
class DateInter extends Pair<Date> {
   @Override
   public Date getValue() {
      return super.getValue();
   }
 
   @Override
   public void setValue(Date value) {
      super.setValue(value);
   }
}

复制代码class Pair {
   private Object value;
 
   public Object getValue() {
      return value;
   }
 
   public void setValue(Object value) {
      this.value = value;
   }
}

复制代码class DateInter extends Pair<java.util.Date> {
  DateInter();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method Pair."<init>":()V
       4: return
 
  public java.util.Date getValue();
    Code:
       0: aload_0
       1: invokespecial #2                  // Method Pair.getValue:()Ljava/lang/Object;
       4: checkcast     #3                  // class java/util/Date
       7: areturn
 
  public void setValue(java.util.Date);
    Code:
       0: aload_0
       1: aload_1
       2: invokespecial #4                  // Method Pair.setValue:(Ljava/lang/Object;)V
       5: return
 
  public void setValue(java.lang.Object);
    Code:
       0: aload_0
       1: aload_1
       2: checkcast     #3                  // class java/util/Date
       5: invokevirtual #5                  // Method setValue:(Ljava/util/Date;)V
       8: return
 
  public java.lang.Object getValue();
    Code:
       0: aload_0
       1: invokevirtual #6                  // Method getValue:()Ljava/util/Date;
       4: areturn
}

复制代码
public function up()
{
    Schema::create('user', function (Blueprint $table) {
        $table->increments('id');
        $table->timestamps();
    });
}


public function down()
{
    Schema::dropIfExists('user');
}

复制代码public function up()
{
    Schema::create('user', function (Blueprint $table) {
        $table->increments('id')->index()->comment('用户id');
        $table->string('name')->default('')->comment('用户名');
        $table->string('email')->nullable()->comment('用户邮箱');
        $table->timestamps();
    });
}

复制代码public function down()
{
    Schema::dropIfExists('user');
}

复制代码
public function up()
{
    Schema::table('user', function (Blueprint $table) {
        Schema::rename('user','users');
    });
}

复制代码public function up()
{
    Schema::table('user', function (Blueprint $table) {
        //
        Schema::rename('users','user');
    });
}

复制代码class UserTableSeeder extends Seeder
{

    public function run()
    {
        DB::table('users')->insert($insertData);
    }
}

复制代码$factory->define(App\User::class, function (Faker $faker) {
    return [
        //
    ];
});

复制代码$factory->define(App\Models\User::class, function (Faker $faker) {
    return [
    	// 直接调用 faker API 生成假数据，更多 faker 相关查看 文档。
        'username' => $faker->name,
        'email' => $faker->unique()->safeEmail,
    ];
});

复制代码
class UserTableSeeder extends Seeder
{

    public function run()
    {
        factory(App\User::class)->times(10)->make()->each(function($user,$index){
        	$user->save();
        });
    }
}