JAVA的Stream

1.初识流

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;public class Start1 {public static void main(String [] args){List<String> list = new ArrayList<>();list.add("王xx");list.add("王x");list.add("奉x");list.add("钱xx");Stream<String> str = list.stream();str.filter(s->s.startsWith("王")).filter(name->name.length()==3).filter(name->name.length()==3).forEach(name-> System.out.println(name));}
}

2.获取流

import java.util.*;
import java.util.stream.Stream;public class CollectionStream {public static void main(String[] args) {List<String>list=new ArrayList<>();Stream<String> stream = list.stream();Set<String> set=new HashSet<>();Stream<String> stream1 = set.stream();Set<String> set1=new LinkedHashSet<>();Stream<String> stream2 = set1.stream();Map<String,String>map=new HashMap<>();Set<String> strings = map.keySet();Stream<String> stream3 = strings.stream();Collection<String> values = map.values();Stream<String> stream4 = values.stream();Set<Map.Entry<String,String>>set2=map.entrySet();Stream<Map.Entry<String, String>> stream5 = set2.stream();Integer []arr=new Integer[10];Stream<Integer>stream6=Stream.of(1,2,3,4,5);Stream<Integer>stream7=Stream.of(arr);}
}

forEach
forEach方法，用来遍历流是一个终结方法，遍历之后不能继续调用Stream流的其他方法

import java.util.stream.Stream;public class StreamForeach {public static void main(String[] args) {Stream<Integer>stream=Stream.of(1,2,3,4,5);stream.forEach(i->System.out.println(i));}
}

Stream filter的使用
延迟方法

import java.util.stream.Stream;
/*
Stream流中常用的方法filter：用与对Stream流中数据过滤
filter*/
public class StreamFilter {public static void main(String[] args) {Stream<Integer>stream=Stream.of(1,3,8,5,1,4,2,7,3,3);stream.filter(i->i%2==0).forEach(i-> System.out.println(i));}
}

Stream map方法的使用
延迟方法

import java.util.stream.Stream;public class StreamMap {public static void main(String[] args) {Stream<Integer>stream=Stream.of(1,2,3,4,5,6);stream.map((i)->{return (char)(i+64);}).forEach((i)-> System.out.println(i));}
}

Stream count方法的使用
终结方法

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;public class StreamCount {public static void main(String[] args) {Stream<Integer>stream=Stream.of(1,3,1,4,5,2,0);long count = stream.count();System.out.println(count);List <Integer>list=new ArrayList<>();list.add(1);list.add(3);list.add(1);list.add(4);list.add(5);list.add(2);list.add(0);System.out.println(list.stream().count());}
}

Stream Limit方法的使用
延时方法

import java.util.stream.Stream;public class StreamLimit {public static void main(String[] args) {Stream<String>stream=Stream.of("D","j","k","s","t","r","a");stream.limit(3).forEach((i)-> System.out.print(i));}
}

Stream skip方法的使用
延时方法

import java.util.stream.Stream;public class StreamSkip {public static void main(String[] args) {Stream<String> stream=Stream.of("D","j","k","s","t","r","a");stream.skip(3).forEach((i)-> System.out.print(i));}
}

Stream concat方法的使用

import java.util.stream.Stream;
public class StreamConcat {public static void main(String[] args) {Stream<String>stream=Stream.of("D","j","k","s","t","r","a");Stream<String>stream1=Stream.of("s","p","f","a");Stream<String> stream2 = Stream.concat(stream, stream1);stream2.forEach((i)-> System.out.print(i));}
}

样例

package Demo;import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;public class Main {public static void main(String[] args) {Person []asd=new Person[10];int k=0;Stream<String> stream = Stream.of("张三","谢五","李四","蓝孔雀","阿达尔","韩佳人");Stream<String> limit = stream.filter((i) -> i.length() == 3).limit(3);Stream<String> stream1=Stream.of("daidioja","dadadafsrfsdq","weASQQEDQD","adad","sadasd");Stream<String> skip = stream1.filter((i) ->i.length()> 6).skip(2);Stream.concat(limit, skip).map((i)->new Person(i)).forEach(i-> System.out.println(i));}
}

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