可变参数JAVA

public class Main {
    public static void main(String[] args) {
 
//方法形参的个数是可以变化的
        //格式：属性类型...名字
        System.out.println(getSum(1,2,3,4,5,6,7,8));
    }
 
 
    //通过键值对对象来遍历；
 
public static int getSum(int a,int...args){//可变参数;
      int sum=0;
        for(int i:args)
      {
          sum+=i;
      }
 
        return sum;
}
 
 
}

可变参数只能有一个数组，不能有两个数组;此外在形参列表中，

可变参数要写在最后；

 stream流

 

 ArrayListlist1=new ArrayList<>();
    list1.add("milan");
    list1.add("manunited");
    list1.add("rmd");
    list1.add("inter");
 
    list1.stream().filter(name->name.startsWith("m")).filter(name->name.length()==3).forEach(name-> System.out.println(name));
 

获取Stream流的方法：根据集合特点有不同的方法，如上

import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.stream.Stream;
 
public class Main {
    public static void main(String[] args) {
 
        //单列集合的获取比较简单；,使用stream方法获取流对象，调用方法即可
    ArrayListlist1=new ArrayList<>();
    Collections.addAll(list1,"inter","milan","FCB","RMD","MCI","MUN","LIV","CHE");
    //获取流
        Streamss=list1.stream();
        //遍历流对象并打印;
        ss.forEach(new Consumer() {
            @Override
            public void accept(String s) {
                System.out.println(s);
            }
        });
        //使用lambda简化
    list1.stream().forEach(name-> System.out.println(name));
    //使用终结方法打印流的数据
    list1.stream().filter(name->name.startsWith("m")).filter(name->name.length()==3).forEach(name-> System.out.println(name));
 
    //双列集合需要先获取单列集合，在操作；也可以使用entryset获取全部
        HashMaphm=new HashMap<>();
        hm.put("aaa",111);
        hm.put("bbb",222);
        hm.put("ccc",333);
        hm.put("ddd",444);
 
        hm.keySet().stream().forEach(new Consumer() {
            @Override
            public void accept(String s) {
                System.out.println(s);
            }
        });
        hm.keySet().stream().forEach(name-> System.out.println(name));
        hm.entrySet().stream().forEach(name-> System.out.println(name));//同时获取键值集合
 
        //数组的流获取
        int[]arr={1,2,3,4,5,6,7,8};
        String[]arr1={"a","b","c","d","e"};
        //获取Stream流
        Arrays.stream(arr).forEach(s-> System.out.println(s));
 
        System.out.println("_____________________________");
        Arrays.stream(arr1).forEach(name-> System.out.println(name));
    }
    //通过键值对对象来遍历；
 
//零散数据
   
}

Stream中间方法

 
import com.sun.management.GarbageCollectionNotificationInfo;
import com.sun.source.tree.Tree;
 
import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Stream;
 
public class Main {
    public static void main(String[] args) {
 
        //单列集合的获取比较简单；,使用stream方法获取流对象，调用方法即可
    ArrayListlist1=new ArrayList<>();
    Collections.addAll(list1,"inter","milan","FCB","RMD","MCI","MUN","LIV","CHE");
 
    list1.stream().filter(new Predicate() {
        @Override
        public boolean test(String s) {
           return  s.startsWith("m");
           // return false;
        }
    }).forEach(new Consumer() {
        @Override
        public void accept(String s) {
            System.out.println(s);
        }
    });
//stream流只能使用一次；最好一次使用完成。
        //修改stream流不会影响原集合；
    list1.stream().filter(s->s.startsWith("M")).forEach(s-> System.out.println(s));
    list1.stream().limit(5).forEach(s-> System.out.println(s));
    list1.stream().limit(5).skip(2).forEach(s-> System.out.println(s));
    //合并流
    Stream.concat(list1.stream(),list1.stream()).forEach(s-> System.out.println(s));
 
    
    }
    //通过键值对对象来遍历；
//零散数据
}

 Stream流终结方法