go复制代码func jieshen(n int) int{
    //计算阶乘的具体方法
}

go复制代码func jieshen(n int) int {
	if n<=2 {
		return n
	}
    //f(n)的通用方法
}

go复制代码 func jieshen(n int) int {
 	if n <= 2 {
 		return n
 	}
 	return n * jieshen(n-1)
 }

go复制代码func f(n int) int {
   
}

go复制代码func f(n int) int {
    if n==1 {
        return 1
    }
}

go复制代码func f(n int) int {
    if n==1 {
        return 1
    }
    return f(n-1)+f(n-2)
}

go复制代码func f(n int) int {
    //f(0) = 0,f(1) = 1，等价于 n<=2时，f(n) = n。
    if n<=2 {
        return n
    }
    return f(n-1)+f(n-2)
}

css复制代码mysql -u root -p

ini复制代码show databases;

ini复制代码use bakery;

sql复制代码show columns from customer;

show columns from product; 

select * from customer;

select * from product;

java复制代码public class LongAccumulatorDemo {



    public static void main(String[] args) throws InterruptedException {

        LongAccumulator accumulator = new LongAccumulator((x, y) -> x + y, 0);

        ExecutorService executor = Executors.newFixedThreadPool(8);

        IntStream.range(1, 11).forEach(i -> executor.submit(() -> accumulator.accumulate(i)));



        Thread.sleep(2000);

        System.out.println(accumulator.getThenReset());

    }

}

java复制代码LongAccumulator accumulator = new LongAccumulator((x, y) -> x + y, 0);

java复制代码accumulator.accumulate(1);

accumulator.accumulate(2);

accumulator.accumulate(3);

...

accumulator.accumulate(8);

accumulator.accumulate(9);

accumulator.accumulate(10);

java复制代码LongAccumulator counter = new LongAccumulator((x, y) -> x + y, 0);

LongAccumulator result = new LongAccumulator((x, y) -> x * y, 0);

LongAccumulator min = new LongAccumulator((x, y) -> Math.min(x, y), 0);

LongAccumulator max = new LongAccumulator((x, y) -> Math.max(x, y), 0);

ini复制代码//list转stream流 List<String> list = new ArrayList<>();     
   Stream<String> listStream = list.stream(); 
   //Set转stream流  Set<String> set = new HashSet<>();   
     Stream<String> setStream = set.stream();   
//map转stream流Map<String, Integer> map = new HashMap<>(); 
     Stream<String> keyStream = map.keySet().stream();     
 Stream<Integer> valueStream = map.values().stream();  
  Stream<Map.Entry<String, Integer>> entryStream = map.entrySet().stream();

sql复制代码//第一种: 使用java.util.Arrays.stream(T[] array)方法用数组创建流   
   int[] array={1,3,5,6,8};       IntStream stream = Arrays.stream(array);   ​//第二种: 可以通过Stream接口的静态方法of(T... values)生成流      String[] strArray = {"hello", "world", "java"};      Stream<String> strArrayStream = Stream.of(strArray);     Stream<String> strArrayStream2 = Stream.of("hello", "world", "java");       Stream<Integer> intStream = Stream.of(10, 20, 30);

ruby复制代码 Stream<String> stringStream = Stream.of("景天", "雪见", "长卿", "紫萱");        stringStream.forEach(System.out::println);         //打印结果: ["景天", "雪见", "长卿", "紫萱"]

rust复制代码List<String> nameList = Arrays.asList("景天", "雪见", "长卿", "紫萱");
nameList.stream().filter(s -> s.startsWith("紫")).forEach(System.out::println);//打印结果: 紫萱

scss复制代码 List<Integer> num = Arrays.asList(1, 2, 3, 4, 5);    num.stream().map(n -> n * 2).forEach(System.out::println);     //打印结果: [2, 4, 6, 8, 10]​

vbnet复制代码 // map 生成的是个 1:1 映射，每个输入元素，都按照规则转换成为另外一个元素。还有一些场景，是一对多映射关系的，这时需要 flatMap       String[] strs = {"java8", "is", "easy", "to", "use"};     List<String[]> distinctStrs = Arrays.stream(strs)     .map(str -> str.split(""))    // 映射成为Stream<String[]>        .distinct().collect(Collectors.toList()); //distinct操作是以 “字符串数组“为单元进行去重        /* 在执行map操作以后，我们得到是一个包含多个字符串数组的流，打印结果如下所示   [j, a, v, a, 8]       [i, s]      [e, a, s, y]         [t, o]         [u, s, e]      */  ​List<String> distinctStr = Arrays.stream(strs)    .map(str -> str.split("")) // 映射成为Stream<String[]>           .flatMap(Arrays::stream)  // 扁平化为Stream<String>       .distinct().collect(Collectors.toList());      ​/* flatMap将由map映射得到的Stream<String[]>，转换成由各个字符串数组映射成的流Stream<String>，        再将这些小的流扁平化成为一个由所有字符串构成的大流Steam<String>，   从而能够达到我们的目的。               打印结果：               [j, a, v, 8, i, s, e, y, t, o, u]     */

ruby复制代码 List<String> limitList = Arrays.asList("景天", "雪见", "长卿", "紫萱");    //取前3个数据在控制台输出       limitList.stream().limit(3).forEach(System.out::println);     //打印结果:["景天", "雪见", "长卿"]

ini复制代码//跳过3个元素,把剩下的元素在控制台输出     List<String> list = Arrays.asList("景天", "雪见", "长卿", "紫萱");   list.stream().skip(3).forEach(System.out::println);    //打印结果:["紫萱"]

vbnet复制代码List<String> concatList1 = Arrays.asList("景天", "雪见", "长卿", "紫萱");   List<String> concatList2 = Arrays.asList("重楼", "茂茂", "必平", "龙葵");     Stream<String> stream1 = concatList1.stream();   Stream<String> stream2 = concatList2.stream();      Stream.concat(stream1, stream2).forEach(System.out::println);   // 打印结果: ["景天", "雪见", "长卿", "紫萱","重楼", "茂茂", "必平", "龙葵"]

ruby复制代码List<String> distinctList = Arrays.asList("景天", "雪见", "长卿", "紫萱", "紫萱", "雪见"); distinctList.stream().distinct().forEach(System.out::println); // 打印结果: ["景天", "雪见", "长卿", "紫萱"]

css复制代码 //题目: 按照字母顺序把数据在控制台输出 sorted()是正序List<String> sortList = Arrays.asList("Lucy", "Jack", "Anny", "Vincent", "Charles","William");sortList.stream().sorted().forEach(System.out::println);//打印结果: [Anny,Charles,Jack,Lucy，Vincent，William] //题目: 按照名称长度顺序从短到长 把数据在控制台输出 sortList.stream().sorted(Comparator.comparingInt(String::length))    .forEach(System.out::println); //打印结果:  [Lucy,Jack,Anny,Vincent,Charles,William]

csharp复制代码  List<String> stringList = new ArrayList<>();        for (int i = 0; i < 10; i++) {         stringList.add("第" + i + "条数据");         }         long parallelStreamNowTime = System.currentTimeMillis();   stringList.parallelStream().forEach(s -> {             try {                       Thread.sleep(1000);          } catch (InterruptedException e) {                 e.printStackTrace();              }     });        long parallelStreamTime = System.currentTimeMillis();      System.out.println("Stream需要时间" + (parallelStreamTime - parallelStreamNowTime));        //打印结果:  Stream需要时间2027

scss复制代码Optional<Integer> findFirst = list.stream().parallel().filter(x->x>6).findFirst();

vbnet复制代码List<String> countList = Arrays.asList("Lucy", "Jack", "Anny", "Vincent","Charles", "William","William"); long count1 = countList.stream().count();System.out.println("总元素个数是:"+count1);  // 打印结果 : 总元素个数是:7 ​long count2 = countList.stream().distinct().count(); System.out.println("去重之后元素个数是:"+count2);  // 打印结果 : 去重之后元素个数是:6

scss复制代码 List<Integer> integerList  = Arrays.asList(1,2,3,4,5); if(integerList.stream().allMatch(i->i>3)){      System.out.println( "值都大于3");  }

scss复制代码 List<Integer> integerList  = Arrays.asList(1,2,3,4,5);  if(integerList.stream().anyMatch(i->i>3)){      System.out.println( "存在大于3的值");  }

scss复制代码List<Integer> integerList  = Arrays.asList(1,2,3,4,5);  if(integerList.stream().noneMatch(i -> i > 3)){      System.out.println("值都小于3"); }

vbnet复制代码List<String> strings = Arrays.asList("abc", "def", "gkh", "abc");//concat 合并流List<String> strings2 = Arrays.asList("xyz", "jqx");​List<String> concatList = Stream.concat(strings2.stream(),strings.stream())    .collect(Collectors.toList());System.out.println(concatList);  //打印结果: [xyz, jqx, abc, def, gkh, abc]

sql复制代码//对数组的统计，比如用List<Integer> number = Arrays.asList(1, 2, 5, 4);IntSummaryStatistics statistics = number.stream().mapToInt((x) -> x).summaryStatistics();System.out.println("列表中最大的数 : "+statistics.getMax());System.out.println("列表中最小的数 : "+statistics.getMin());System.out.println("平均数 : "+statistics.getAverage());System.out.println("所有数之和 : "+statistics.getSum());

ruby复制代码 List<String> list1 = Arrays.asList("A1", "B1", "C1", "A2", "B2", "C2", "A3", "B3","C3");  for(int i=0;i<10;i++) {     Optional<String> c = list1.stream().filter(s -> s.contains("A")).findAny();   System.out.println("====串行流findAny()======" + c.get());  } //打印结果:  //  ====串行流findAny()======A1 //  ====串行流findAny()======A1 //  ====串行流findAny()======A1  //  ====串行流findAny()======A1  //  ====串行流findAny()======A1  //  ====串行流findAny()======A1 //  ====串行流findAny()======A1  //  ====串行流findAny()======A1  //  ====串行流findAny()======A1 //  ====串行流findAny()======A1

ruby复制代码List<String> list1 = Arrays.asList("A1", "B1", "C1", "A2", "B2", "C2", "A3", "B3","C3"); Optional<String> a = list1.parallelStream().filter(s -> s.contains("A")).findAny(); System.out.println("====findAny()======" + a.get()); ​//打印结果:  每次执行打印的是A1或者A2或者A3中任意一个 // ====并行流findAny()======A3// ====并行流findAny()======A3 // ====并行流findAny()======A2 // ====并行流findAny()======A1 // ====并行流findAny()======A1 // ====并行流findAny()======A2 // ====并行流findAny()======A3 // ====并行流findAny()======A3 // ====并行流findAny()======A3 // ====并行流findAny()======A2

less复制代码List<String> list2 = Arrays.asList("A1", "B1", "C1", "A2", "B2", "C2", "A3", "B3","C3"); Optional<String> b = list2.parallelStream().filter(s -> s.contains("B")).findFirst(); System.out.println("====findFirst()====" + b.get());// 打印结果:   ====findFirst()====B1

vbnet复制代码//获取String集合中最长的元素。List<String> maxList = Arrays.asList("Lucy", "Jack", "Anny", "Vincent","Charles","William");Optional<String> max = maxList.stream().    max(Comparator.comparing(String::length));System.out.println("最长的字符串:" + max.get());//打印结果: 最长的字符串:Vincent

vbnet复制代码List<Integer> reduceList = Arrays.asList(1, 3, 2, 8, 11, 4);  // 求和方式1 Optional<Integer> sum = reduceList.stream().reduce((x, y) -> x + y); // 求和方式2 Optional<Integer> sum2 = reduceList.stream().reduce(Integer::sum); // 求和方式3 Integer sum3 = reduceList.stream().reduce(0, Integer::sum);​  // 求乘积  Optional<Integer> product = reduceList.stream().reduce((x, y) -> x * y);​  // 求最大值方式1  Optional<Integer> max2 = reduceList.stream().reduce((x, y) -> x > y ? x : y);  // 求最大值写法2  Integer max3 = reduceList.stream().reduce(1, Integer::max);​  System.out.println("list求和：" + sum.get() + "," + sum2.get() + "," + sum3);  //打印结果:  list求和：29,29,29  System.out.println("list求积：" + product.get());  //打印结果:  list求积：2112  System.out.println("list求最大值：" + max2.get() + "," + max3);  //打印结果: list求最大值：11,11

vbnet复制代码 // 如何把list集合拼接成以逗号分隔的字符串 a,b,c List<String> list = Arrays.asList("a", "b", "c");​// 第一种方法，可以用stream流 String join = list.stream().collect(Collectors.joining(",")); System.out.println(join); // 输出 a,b,c​ // 第二种方法，其实String也有join方法可以实现这个功能,合并数组为单一字符串，可传分隔符 String join1 = String.join(",", list); System.out.println(join1); // 输出 a,b,c

perl复制代码String str = "I love JavaAlliance forever";// 1、删除字符串中指定字符，返回一个stringString remove = StringUtils.remove(str, "forever"); // 移除字符串中的 foreverSystem.out.println(remove); // 打印结果是  I love JavaAlliance​// 2、将字符串反转，返回一个stringString reverse = StringUtils.reverse(str);System.out.println(reverse); // 打印结果是  reverof ecnaillAavaJ evol I​// 3、比较两个字符串是否相等,如果两个均为null，则也认为相等StringUtils.equals("Java", "Java"); // 结果是trueStringUtils.equals("", ""); // 结果是trueStringUtils.equals(null, null); // 结果是trueStringUtils.equals(null, ""); // 结果是falseStringUtils.equals("", null); // 结果是falseStringUtils.equals(null, ""); // 结果是falseStringUtils.equalsIgnoreCase("java", "JAVA"); // 不区分大小写--结果是true​// 4、重复拼接字符串String str1 = StringUtils.repeat("ab", 2);System.out.println(str1); // 输出abab​// 5、首字母转成大写String str2 = "javaAlliance";String capitalize = StringUtils.capitalize(str2);System.out.println(capitalize); // 输出JavaAlliance​// 6、字符串固定长度填充StringUtils.leftPad("test", 8, "0"); // 字符串固定长度 8位，若不足，往左补 0StringUtils.rightPad("test", 8, "0"); // 字符串固定长度 8位，若不足，往右补 0​// 7、字符串关键字替换StringUtils.replace("aba", "a", "z")   = "zbz"; // 默认替换所有关键字StringUtils.replaceOnce("aba", "a", "z")   = "zba";// 替换关键字，仅替换一次StringUtils.replacePattern("ABCabc123", "[^A-Z0-9]+", "")   = "ABC123"; // 使用正则表达式替换​// 8、将数组拼接成字符串StringUtils.join(["a", "b", "c"], ",") ; //拼接结果是  "a,b,c"​// 9、字符串拆分StringUtils.split("a..b.c", '.')  //拆分结果是 ["a", "b", "c"]StringUtils.splitByWholeSeparatorPreserveAllTokens("a..b.c", ".")  //拆分结果是 ["a","", "b", "c"]​​​​

perl复制代码User user = new User();user.setUserName("JavaAlliance").setEmail("196432@qq.com");// 对象转mapMap<String, String> map = BeanUtils.describe(user);System.out.println(map); // 输出// map转对象User newUser = new User();BeanUtils.populate(newUser, map);System.out.println(newUser); // 输出

vbnet复制代码// Date类型转String类型String date = DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss");System.out.println(date); // 输出 2021-05-01 01:01:01​// String类型转Date类型   该方法会将日期字符串按照第二参数中的String数组，依次比对，选择合适的Pattern来解析。Date date1 = DateUtils.parseDate("2021-05-01 01:01:01", new String[]{"yyyy-MM-dd HH:mm:ss"});​Date now = new Date();// Date 加 1 天Date addDays = DateUtils.addDays(now, 1);// Date 加 33 分钟Date addMinutes = DateUtils.addMinutes(now, 33);// Date 减去 233 秒Date addSeconds = DateUtils.addSeconds(now, -233);// 判断是否 Wie 同一天boolean sameDay = DateUtils.isSameDay(addDays, addMinutes);// 过滤时分秒,若 now 为 2020-05-07 22:13:00 调用 truncate 方法以后// 返回时间为 2020-05-07 00:00:00Date truncate = DateUtils.truncate(now, Calendar.DATE);​

sql复制代码Date now = new Date();// Date转成LocalDateTime 这里指定使用当前系统默认时区LocalDateTime localDateTime = now.toInstant().atZone(ZoneId.systemDefault())    .toLocalDateTime();​// LocalDateTime转成Date 这里指定使用当前系统默认时区Date date = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());​// 按照 yyyy-MM-dd HH:mm:ss 转化时间LocalDateTime dateTime = LocalDateTime.parse("2020-05-07 22:34:00", DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));​// 将 LocalDateTime 格式化字符串String format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").format(dateTime);​//LocalDateTime 获取当前时间年份，月份LocalDateTime now = LocalDateTime.now();// 年int year = now.getYear();// 月int month = now.getMonthValue();// 日int day = now.getDayOfMonth();​// LocalDateTime 进行日期加减，获取下一天的时间LocalDateTime now = LocalDateTime.now();// 当前时间加一天LocalDateTime plusDays = now.plusDays(1l);// 当前时间减一个小时LocalDateTime minusHours = now.minusHours(1l);// 还有很多其他方法​

ruby复制代码String[] arrayA = new String[]{"1", "2", "3", "4"};String[] arrayB = new String[]{"3", "4", "5", "6"};List<String> listA = Arrays.asList(arrayA);List<String> listB = Arrays.asList(arrayB);// 1、并集 unionSystem.out.println(CollectionUtils.union(listA, listB));// 输出: [1, 2, 3, 4, 5, 6]​// 2、交集 intersectionSystem.out.println(CollectionUtils.intersection(listA, listB));// 输出:[3, 4]​// 3、交集的补集（析取）disjunctionSystem.out.println(CollectionUtils.disjunction(listA, listB));// 输出:[1, 2, 5, 6]​// 4、差集（扣除）System.out.println(CollectionUtils.subtract(listA, listB));// 输出:[1, 2]​​  // 1、交集 List<String> intersectionList = new ArrayList<>(listA); intersectionList.retainAll(listB); System.out.println(intersectionList); // 输出:[3, 4]​ // 2、差集 List<String> differenceList = new ArrayList<>(listA); differenceList.removeAll(listB); System.out.println(differenceList); // 输出:[1, 2]​// 3、并集 (先做差集再做添加所有）List<String> unionList = new ArrayList<>(listA);unionList.removeAll(listB); // unionList [1, 2]unionList.addAll(listB); // 添加[3,4,5,6]System.out.println(unionList);// 输出:[1, 2, 3, 4, 5, 6]​

vbnet复制代码 String str = "张三 李四 李四 王五 王五 王五"; String[] strArr = str.split(" "); List<String> words = new ArrayList<>(Arrays.asList(strArr));//创建一个HashMultiset集合，并将words集合数据放入 Multiset<String> wordMultiset = HashMultiset.create(); wordMultiset.addAll(words);//将不同的元素放在一个集合set中 for (String key : wordMultiset.elementSet()) {   //查看指定元素的个数   System.out.println(key + "-->" + wordMultiset.count(key));     //打印结果:  李四-->2    张三-->1   王五-->3 }

vbnet复制代码Multimap<String, String> myMultimap = ArrayListMultimap.create();myMultimap.put("Fruits", "Bannana");myMultimap.put("Fruits", "Apple");myMultimap.put("Fruits", "Pear");myMultimap.put("Fruits", "Pear");myMultimap.put("Vegetables", "Carrot");​// 查询Multimap中的存储的元素个数System.out.println(myMultimap.size()); // 打印结果: 5​//查询键为“Fruits”所对应的valueCollection<String> fruits = myMultimap.get("Fruits");System.out.println(fruits);//打印结果:  [Bannana, Apple, Pear, Pear]Collection<String> vegetables = myMultimap.get("Vegetables");System.out.println(vegetables); //打印结果: [Carrot]​// 循环迭代遍历整个 Multimap里存储的value值for (String value : myMultimap.values()) {    System.out.println(value);      //打印结果:      //Carrot      //Bannana      //Apple      //Pear      //Pear }​//移除其中一个元素myMultimap.remove("Fruits", "Pear");System.out.println(myMultimap.get("Fruits"));//打印结果: [Bannana, Apple, Pear]​//将键为"Fruits"所对应的value内容替换为集合  Arrays.asList("178","910","123")//返回的oldValues是之前的旧值Collection<String> oldValues = myMultimap.replaceValues("Fruits", Arrays.asList("178","910","123"));​System.out.println("oldValues="+oldValues);//打印结果: oldValues=[Bannana, Apple, Pear]System.out.println("myMultimap="+myMultimap);//打印结果: myMultimap={Vegetables=[Carrot], Fruits=[178, 910,123]}​//移除Multimap中键为“Fruits”的所有元素myMultimap.removeAll("Fruits");System.out.println(myMultimap.get("Fruits"));//打印结果: []

vbnet复制代码//双向mapBiMap<Integer,String> biMap=HashBiMap.create();biMap.put(1,"张三");biMap.put(2,"李四");biMap.put(3,"王五");biMap.put(4,"赵六");biMap.put(5,"李七");biMap.put(4,"小小");​//通过key值得到value值(注意key里面的类型根据泛行String value= biMap.get(1);System.out.println("id为1的value值 --"+value); //打印结果: id为1的value值 --张三​//通过value值得到key值int key= biMap.inverse().get("张三");System.out.println("value为张三的key值 --"+key); //打印结果: value为张三的key值 --1​//通过key值重复，那么vakue值会被覆盖。String valuename= biMap.get(4);System.out.println("id为4的value值 --"+valuename);//打印结果: id为4的value值 --小小

vbnet复制代码// 按照指定文件后缀如java,txt等去查找指定文件夹下的文件File directory = new File("E:\\test");FileUtils.listFiles(directory, new String[]{"txt"}, false);

ini复制代码// 读取指定文件所有行 不需要使用 while 循环读取流了List<String> lines = FileUtils.readLines(fileA)

vbnet复制代码// 1、 向一个文件写入一段文字FileUtils.write(new File("D:/a/1.txt"), "文件内容", "UTF-8", true);    // 2、以追加的方式写入FileUtils.writeStringToFile(new File("D:/a/1.txt"), "author：apple", "UTF-8", true);    //3、写入多行List<String> list= new ArrayList<String>();list.add("第一行");list.add("第二行");FileUtils.writeLines(new File("D:/a/1.txt"), list, true);

vbscript复制代码//读文件  System.out.println(FileUtils.readFileToString(new File("D:/a/1.txt"), "UTF-8"));​//返回一个list System.out.println(FileUtils.readLines(new File("D:/a/1.txt"), "UTF-8"));

sql复制代码// 删除文件夹 FileUtils.deleteDirectory(new File("D:/a"));        // 文件夹不是空仍然可以被删除，永远不会抛出异常  FileUtils.deleteQuietly(new File("D:/a"));

sql复制代码//结果是a和a1在同一目录  FileUtils.copyDirectory(new File("D:/a"), new File("D:/a1"));   ​//结果是将a拷贝到a2下  FileUtils.copyDirectoryToDirectory(new File("D:/a"), new File("D:/a2"));        //拷贝文件  方式1 FileUtils.copyFile(new File("d:/1.xml"), new File("d:/1.xml.bak"));  //拷贝文件  方式2Writer write = new FileWriter("D：/abc_bak.txt");InputStream ins = new FileInputStream(new File("D：/abc.txt"));IOUtils.copy(ins, write);write.close();IOUtils.closeQuietly(ins);​​//拷贝文件到目录中  FileUtils.copyFileToDirectory(new File("d:/1.xml"), new File("d:/a"));      //拷贝url到文件  FileUtils.copyURLToFile(new URL("http://www.a.com/1.xml"), new File("d:/1.xml"));//可实现快速下载URL url = new URL("http://hzf-image-test.oss-cn-beijing.aliyuncs.com/hr_image/HF306268301810/1513632067664AbIB40pv_defalut.JPG?x-oss-process=image/resize,h_400");File file = new File("/Users/jjs/Desktop/pic.jpg");FileUtils.copyURLToFile(url, file);

sql复制代码//移动文件 或 文件夹  //static void moveDirectory(File srcDir, File destDir)   FileUtils.moveDirectory(new File("D:/a1"), new File("D:/a2")); //注意这里 第二个参数文件不存在会引发异常      //static void moveDirectoryToDirectory(File src, File destDir, boolean createDestDir)   FileUtils.moveDirectoryToDirectory(new File("D:/a2"), new File("D:/a3"), true);      /* 上面两个方法的不同是：  * moveDirectory：D:/a2里的内容是D:/a1的内容。  * moveDirectoryToDirectory：D:/a2文件夹移动到到D:/a3里  */

vbnet复制代码//下载方式1URL url = new URL("http://www.baidu.com/img/baidu_logo.gif");File file = new File("/Users/jjs/Desktop/baidu1.gif");FileUtils.copyURLToFile(url, file);    //下载方式2InputStream in = new URL("http://www.baidu.com/img/baidu_logo.gif").openStream();byte[] gif = IOUtils.toByteArray(in);FileUtils.writeByteArrayToFile(new File("D：/baidu2.gif"), gif);IOUtils.closeQuietly(in);​//下载方式3InputStream in3 = new URL("http://www.baidu.com/img/baidu_logo.gif").openStream();byte[] gif3 = IOUtils.toByteArray(in3);IOUtils.write(gif3, new FileOutputStream(new File("D：/baidu3.gif")));IOUtils.closeQuietly(in3);

c复制代码#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"

int
main(int argc, char *argv[])
{
  int ticks;  // time to sleep

  if(argc <= 1){
    fprintf(2, "usage: sleep ticks\n");
    exit(1);
  }
  ticks = atoi(argv[1]);

  sleep(ticks);

  exit(0);
}

sh复制代码$ make qemu
...
init: starting sh
$ sleep 10
(nothing happens for a little while)
$

c复制代码#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"

int
main(int argc, char *argv[])
{
	int p[2];  // file descriptors for pipe
	char recv_buf[128];

	pipe(p);

	if (fork() == 0) {  // child
		read(p[0], recv_buf, 4);
		close(p[0]);

		printf("%d: received %s\n", getpid(), recv_buf);

		write(p[1], "pong", 4);
		close(p[1]);

		exit(0);
	} else {  // parent
		write(p[1], "ping", 4);
		close(p[1]);

		read(p[0], recv_buf, 4);
		close(p[0]);

		printf("%d: received %s\n", getpid(), recv_buf);

		exit(0);
	}
}

sh复制代码$ make qemu
...
init: starting sh
$ pingpong
4: received ping
3: received pong

c复制代码#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"

#define MAX 36
#define FIRST_PRIME 2

int generate_natural();  // -> out_fd
int prime_filter(int in_fd, int prime);  // -> out_fd

int
main(int argc, char *argv[])
{
	int prime; 
	
	int in = generate_natural();
	while (read(in, &prime, sizeof(int))) {
		// printf("prime %d: in_fd: %d\n", prime, in);  // debug
		printf("prime %d\n", prime); 
		in = prime_filter(in, prime);
	}

	exit(0);
}

// 生成自然数: 2, 3, 4, ..< MAX
int
generate_natural() {
	int out_pipe[2];
	
	pipe(out_pipe);

	if (!fork()) {
		for (int i = FIRST_PRIME; i < MAX; i++) {
			write(out_pipe[1], &i, sizeof(int));
		}
		close(out_pipe[1]);

		exit(0);
	}

	close(out_pipe[1]);

	return out_pipe[0];
}

// 素数筛
int 
prime_filter(int in_fd, int prime) 
{
	int num;
	int out_pipe[2];

	pipe(out_pipe);

	if (!fork()) {
		while (read(in_fd, &num, sizeof(int))) {
			if (num % prime) {
				write(out_pipe[1], &num, sizeof(int));
			}
		}
		close(in_fd);
		close(out_pipe[1]);
		
		exit(0);
	}

	close(in_fd);
	close(out_pipe[1]);

	return out_pipe[0];
}

sh复制代码$ primes
prime 2
prime 3
prime 5
prime 7
prime 11
prime 13
prime 17
prime 19
prime 23
prime 29
prime 31

c复制代码#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/fs.h"
#include "kernel/fcntl.h"

char*
fmtname(char *path)
{
	char *p;

	// Find first character after last slash.
	for(p=path+strlen(path); p >= path && *p != '/'; p--)
		;
	p++;

	return p;
}

void
find(char *path, char *targetname) 
{
	char buf[512], *p;
	int fd;
	struct dirent de;
	struct stat st;

	if (!strcmp(fmtname(path), targetname)) {
		printf("%s\n", path);
	}

	if ((fd = open(path, O_RDONLY)) < 0) {
		fprintf(2, "find: cannot open [%s], fd=%d\n", path, fd);
		return;
	}

	if (fstat(fd, &st) < 0) {
		fprintf(2, "find: cannot stat %s\n", path);
		close(fd);
		return;
	}

	if (st.type != T_DIR) {
		close(fd);
		return;
	}

	// st.type == T_DIR
	
	if (strlen(path) + 1 + DIRSIZ + 1 > sizeof buf) {
		printf("find: path too long\n");
		close(fd);
		return;
	}
	strcpy(buf, path);
	p = buf+strlen(buf);
	*p++ = '/';
	while (read(fd, &de, sizeof(de)) == sizeof(de)) {
		if (de.inum == 0)
			continue;
		memmove(p, de.name, DIRSIZ);
		p[DIRSIZ] = 0;
		
		if (!strcmp(de.name, ".") || !strcmp(de.name, ".."))
			continue;

		find(buf, targetname);
	}
	close(fd);
}

int
main(int argc, char *argv[])
{
	if(argc < 3){
		fprintf(2, "usage: find path filename\n");
		exit(1);
	}

	find(argv[1], argv[2]);

	exit(0);
}

sh复制代码$ echo > b
$ mkdir a
$ echo > a/b
$ find . b
./b
./a/b

sh复制代码$ echo hello too | xargs echo bye
bye hello too
$

sh复制代码$ echo "1\n2" | xargs -n 1 echo line
line 1
line 2
$

sh复制代码$ find . b | xargs grep hello

c复制代码#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/param.h"  // MAXARG

#define is_blank(chr) (chr == ' ' || chr == '\t') 

int
main(int argc, char *argv[])
{
	char buf[2048], ch;
	char *p = buf;
	char *v[MAXARG];
	int c;
	int blanks = 0;
	int offset = 0;

	if(argc <= 1){
		fprintf(2, "usage: xargs <command> [argv...]\n");
		exit(1);
	}

	for (c = 1; c < argc; c++) {
		v[c-1] = argv[c];
	}
	--c;

	while (read(0, &ch, 1) > 0) {
		if (is_blank(ch)) {
			blanks++;
			continue;
		}

		if (blanks) {  // 之前有过空格
			buf[offset++] = 0;

			v[c++] = p;
			p = buf + offset;

			blanks = 0;
		}

		if (ch != '\n') {
			buf[offset++] = ch;
		} else {
			v[c++] = p;
			p = buf + offset;

			if (!fork()) {
				exit(exec(v[0], v));
			}
			wait(0);
			
			c = argc - 1;
		}
	}

	exit(0);
}

sh复制代码$ echo hello too | xargs echo bye
bye hello too
$ find . b
./b
./a/b
$ find . b | xargs echo hello
hello ./b
hello ./a/b

java复制代码/**
 *@description: TODO 
 *@author: HUALEI
 *@date: 2021-11-21
 *@time: 19:29
 */
@Data
public class ProvinceExcelVO implements Serializable {

    private static final long serialVersionUID = 877981781678377000L;

    /**
     * 省份
     */
    private String province;

    /**
     * 省份的简称
     */
    private String abbr;

    /**
     * 省份的面积（km²）
     */
    private Integer area;

    /**
     * 省份的人口（万）
     */
    private BigDecimal population;

    /**
     * 省份的著名景点
     */
    private String attraction;

    /**
     * 省会的邮政编码
     */
    private String postcode;

    /**
     * 省会名
     */
    private String city;

    /**
     * 省会的别名
     */
    private String nickname;

    /**
     * 省会的气候类型
     */
    private String climate;

    /**
     * 省会的车牌号
     */
    private String carcode;
}

java复制代码/**
 * 获取所有省份详情信息
 *
 * @return 导出 Excel 数据源
 */
List<ProvinceExcelVO> getAllProvinceDetails();

/**
 * 将省份详请信息以 Excel 的形式写出到客户端
 *
 * @param response HttpServletResponse 对象
 * @param dataSource 省份详情信息数据源
 * @param fileName 文件名
 * @param sheetName sheet 工作表名
 *
 * @throws IOException IO 流异常
 */
void exportProvinceDetailsExcel(HttpServletResponse response, List<ProvinceExcelVO> dataSource, String fileName, String sheetName) throws IOException;

java复制代码@Override
public List<ProvinceExcelVO> getAllProvinceDetails() {
    List<Province> provinces = this.provinceMapper.selectByAll(new Province());

    if (CollUtil.isNotEmpty(CollUtil.removeNull(provinces))) {
        return provinces.stream()
                .map(p -> {
                    ProvinceExcelVO provinceExcelVO = new ProvinceExcelVO();
                    BeanUtil.copyProperties(p, provinceExcelVO);
                    BeanUtil.copyProperties(p.getCapital(), provinceExcelVO);
                    return provinceExcelVO;
                }).collect(Collectors.toList());
    }
    return null;
}

java复制代码@Override
public void exportProvinceDetailsExcel(HttpServletResponse response, List<ProvinceExcelVO> dataSource, String fileName, String sheetName) throws IOException {
    // 默认创建 xls 格式, 通过 isXlsx => true 创建 xlsx 格式
    // ExcelUtil.getWriter(true);
    ExcelWriter excelWriter = ExcelUtil.getBigWriter();

    // 设置表头别名
    excelWriter.addHeaderAlias("province", "省份名称");
    excelWriter.addHeaderAlias("abbr", "简称");
    excelWriter.addHeaderAlias("area", "面积（km²）");
    excelWriter.addHeaderAlias("population", "人口数量（万）");
    excelWriter.addHeaderAlias("attraction", "著名景点");
    excelWriter.addHeaderAlias("postcode", "邮政编码");
    excelWriter.addHeaderAlias("city", "省会城市");
    excelWriter.addHeaderAlias("nickname", "别称");
    excelWriter.addHeaderAlias("climate", "气候类型");
    excelWriter.addHeaderAlias("carcode", "车牌号");
    
    ......
    ......
}

java复制代码
    excelWriter.write(dataSource, true);
    
    // response 为 HttpServletResponse 对象
    response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8");
    
    // 中文文件名编码
    fileName = URLEncoder.encode(fileName, CharsetUtil.UTF_8) + ".xlsx";
    response.setHeader("Content-Disposition","attachment;filename="+ fileName);
    // 设置 Sheet 工作表名称
    excelWriter.renameSheet(sheetName);
    
    ServletOutputStream out = response.getOutputStream();
    excelWriter.flush(out, true);

    // 关闭 writer，释放内存
    excelWriter.close();
    // 关闭输出 Servlet 流
    IoUtil.close(out);

java复制代码@GetMapping("provinces/excel/export")
public void provincesExcelExport(HttpServletResponse response) throws IOException {
    // 获取数据源
    List<ProvinceExcelVO> provinceExcelList = this.provinceService.getAllProvinceDetails();
    // 导出文件名
    String fileName = "导出省份信息";
    // Sheet 工作表名称
    String sheetName = "省份表";
    // 导出 Excel
    this.provinceService.exportProvinceDetailsExcel(response, provinceExcelList, fileName, sheetName);
}

java复制代码
// 获取 sheet 表
SXSSFSheet sheet = (SXSSFSheet) excelWriter.getSheet();

java复制代码
// 开启跟踪工作表中的所有列，以便自动调整大小
sheet.trackAllColumnsForAutoSizing();

// 列宽自适应，只有开启后才会生效
excelWriter.autoSizeColumnAll();

java复制代码
// 获取表头行，作为数据的所属列
if (sheet.getRow(1) != null) {
    // 获取表头已定义单元格的数目
    int physicalNumberOfCells = sheet.getRow(1).getPhysicalNumberOfCells();
    for (int i = 0; i < physicalNumberOfCells; i++) {
        // 对已定义的每一列设置列宽，解决中文自适应宽度不足的问题
        sheet.setColumnWidth(i, sheet.getColumnWidth(i) * 17 / 10);
    }
}

ini复制代码EventLoopGroup group = new NioEventLoopGroup();
EventLoopGroup group = new DefaultEventLoopGroup( );

java复制代码public static void main(String[] args) {
        EventLoopGroup group1 = new NioEventLoopGroup(3);
        EventLoopGroup group2 = new DefaultEventLoopGroup(2);


        System.out.println(group1.next());
        System.out.println(group2.next());

        group1.next().execute(()->{
            for (int i = 0; i < 10; i++) {
                System.out.println(Thread.currentThread().getName()+"hello "+i);
            }
        });


        group2.next().scheduleAtFixedRate(()->{
            System.out.println(Thread.currentThread().getName()+"  hello2");
        },0,1, TimeUnit.SECONDS);

        group1.shutdownGracefully();
        group2.shutdownGracefully();

    }

java复制代码public class HelloServer {
    public static void main(String[] args) {
        new ServerBootstrap()
                .group(new NioEventLoopGroup(3))
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel nioSocketChannel) throws Exception {//添加handler
                        nioSocketChannel.pipeline().addLast(new StringDecoder());
                        nioSocketChannel.pipeline().addLast(new SimpleChannelInboundHandler<String>() {
                            @Override
                            protected void channelRead0(ChannelHandlerContext channelHandlerContext, String s) throws Exception 							{
                                System.out.println(Thread.currentThread().getName()+"  "+s);
                            }
                        });
                    }
                }).bind(8080);
    }
}

java复制代码public class HelloClient {
    public static void main(String[] args) throws InterruptedException {
        new Bootstrap()
                .group(new NioEventLoopGroup())
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel channel) throws Exception {
                        channel.pipeline().addLast(new StringEncoder());
                    }
                })
                .connect(new InetSocketAddress("localhost", 8080))
                .sync()
                .channel()
                .writeAndFlush("hello world"+"  "+Thread.currentThread().getName());
    }
}

java复制代码public class MyServer {
        public static void main(String[] args) {
            new ServerBootstrap()
                    .group(new NioEventLoopGroup(1), new NioEventLoopGroup(2))
            
				...
        }
    }

java复制代码public class MyServer {
    public static void main(String[] args) {
        EventLoopGroup group = new DefaultEventLoopGroup(3);

        new ServerBootstrap()
                .group(new NioEventLoopGroup(), new NioEventLoopGroup(2))
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        socketChannel.pipeline().addLast("nioHandler",new ChannelInboundHandlerAdapter(){

                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                                ByteBuf buf = (ByteBuf) msg;
                                System.out.println("nioHandler"+Thread.currentThread().getName() + " " + buf.toString(StandardCharsets.UTF_8));
                                // 将消息传递给下一个handler
                                ctx.fireChannelRead(msg);
                            }
                        }).addLast(group,"myhandler",new ChannelInboundHandlerAdapter(){
                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                                ByteBuf buf = (ByteBuf) msg;
                                Thread.sleep(5000);
                                System.out.println("myhandler"+Thread.currentThread().getName() + " " + buf.toString(StandardCharsets.UTF_8));
                            }
                        });
                    }
                })
                .bind(8080);
    }
}

java复制代码static void invokeChannelRead(final AbstractChannelHandlerContext next, Object msg) {
    final Object m = next.pipeline.touch(ObjectUtil.checkNotNull(msg, "msg"), next);
    
    EventExecutor executor = next.executor(); // 获得下一个EventLoop, excutor 即为 EventLoopGroup
    
    // 如果下一个EventLoop 在当前的 EventLoopGroup中
    if (executor.inEventLoop()) {//当前handler中的线程是否和eventloop是同一个线程
        // 使用当前 EventLoopGroup 中的 EventLoop 来处理任务
        next.invokeChannelRead(m);
    } else {
        // 否则让另一个 EventLoopGroup 中的 EventLoop 来创建任务并执行
        executor.execute(new Runnable() {//此时需要在下一个线程中执行
            public void run() {
                next.invokeChannelRead(m);
            }
        });
    }
}