Stream流

获取流

public class Streamdemo {public static void main(String[] args) {//所有集合都可以直接创建流List<String> names = new ArrayList<>();Set<String> nameset = new HashSet<>();Stream<String> name =names.stream();Stream<String> nameset1 =nameset.stream();System.out.println(name);//map创建流Map<String,Integer> maps = new HashMap<>();// 键流Stream<String> mapString = maps.keySet().stream();// 值流Stream<Integer> mapValue= maps.values().stream();// 键值对流Stream<Map.Entry<String, Integer>> keyandvalue =  maps.entrySet().stream();//数组流String[] strlist = {"a","b","c"};Stream<String> str1 = Stream.of(strlist);Stream<String> str2 = Arrays.stream(strlist);}
}

常用api


import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Stream;public class Streamdeom2 {public static void main(String[] args) {List<String> list = new ArrayList<>();List<String> list1 = new ArrayList<>();Collections.addAll(list,"张*","张**","张***","张****");Collections.addAll(list1,"王*","王**","王***","王****");
//        list.stream().findFirst()list.stream().limit(3).forEach(s->System.out.println(s)); //前三位list.stream().skip(3).forEach(s->System.out.println(s)); //跳过前三位list.stream().filter(s -> s.startsWith("张")).forEach(s->System.out.println(s)); //过滤list.stream().distinct().forEach(s->System.out.println(s)); // 去重list.stream().map(s -> "加工后" + s).forEach(s -> System.out.println(s));  //加工方法list.stream().map(s -> new Student(s)).forEach(s -> System.out.println(s)); //加工到某个对象list.stream().map(Student::new).forEach(System.out::println); //与上一行一致，构造器引用Stream<String> newlist = list.stream();Stream<String> newlis1 = list1.stream();Stream.concat(newlist,newlis1).forEach(s -> System.out.println(s));  //合并流list.stream().sorted((e1,e2)->Double.compare(e1.getMoney() , e2.getMoney()))  //排序list.stream().max((e1,e2)->Double.compare(e1.getMoney() , e2.getMoney())) //取最大值}
}
class Student{private String name;public Student(){};@Overridepublic String toString() {return "Student{" +"name='" + name + '\'' +'}';}public Student(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

收集成数组或集合


public class tolistdemo {public static void main(String[] args) {List<String> list = new ArrayList<>();Collections.addAll(list,"王*","王**","王***","王****");Stream<String>  newstream = list.stream().filter(s -> s.startsWith("王"));List<String> list2 = newstream.collect(Collectors.toList()); //转成可变listlist2.add("java");System.out.println(list2);
//        List<String> list2 = newstream.tolist() //转成不可变listStream<String>  newstream1 = list.stream().filter(s -> s.startsWith("王"));Set<String> set1 = newstream1.collect(Collectors.toSet()); //转成setSystem.out.println(set1);Stream<String>  newstream2 = list.stream().filter(s -> s.startsWith("王"));Object[] list3 = newstream2.toArray(); //转成数组System.out.println(Arrays.toString(list3));}
}

异常捕获


public class Trydemo {public static void main(String[] args) {String str = null;try {pritnlen(str);} catch (Exception e) {e.printStackTrace();System.out.println("统一使用捕获所有异常，其他异常捕获了解即可");}finally{System.out.println("最后必执行");}}public static void pritnlen(String s){System.out.println(s.length());}
}

自定义异常捕获

public class Test {public static void main(String[] args) throws defineException {praseint(1);praseint1(-1);}public static void praseint(double d) throws defineException {if(d<0 || d>200){throw new defineException("编译时有异常，且需要把异常throws往上抛");}else {System.out.println("数据正确");}}public static void praseint1(double d) {if(d<0 || d>200){throw new definerunException("运行时有异常，异常throws可不往上抛");}else {System.out.println("数据正确2");}}
}

自动释放资源

package com.ruqi;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;public class Filecopy {public static void main(String[] args) {filecopy("D:\\KwDownload\\song\\新建文本文档.txt","D:\\zhengqinjie\\新建文件夹\\1建.txt");}private static void filecopy(String tagetFile, String afterCopyFile) {//try(资源对象){}try (InputStream in = new FileInputStream(tagetFile);OutputStream out = new FileOutputStream(afterCopyFile);){byte[] buffer = new byte[1024];int len;while ((len = in.read(buffer)) != -1) {out.write(buffer, 0, len);}System.out.println("复制完成");}catch (Exception e ){e.printStackTrace();}}
}

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Java-Stream流，异常捕获

Stream流

获取流

常用api

异常捕获

自定义异常捕获

自动释放资源

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