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));
    }
}