java 8 循环操作List/Map

墨蓝 2022-09-26 03:13 267阅读 0赞

package com.ven.java8.foreach;
    
    import java.util.ArrayList;
    import java.util.LinkedHashMap;
    import java.util.List;
    import java.util.Map;
    
    import com.ven.java8.method.references.CreateFactory;
    
    /**
     * 测试使用java8 操作List/Map
     * 
     * @author xiaowen
     *
     */
    public class TestCollections {
    	public static void main(String[] args) {
    		// 操作Map部分
    		Map<String, Integer> items = new LinkedHashMap<>();
    		items.put("小白", 10);
    		items.put("小文", 20);
    		items.put("小君", 30);
    		items.put("KD", 40);
    		items.put("ws", 50);
    		items.put("XJ", 60);
    		for (Map.Entry<String, Integer> entry : items.entrySet()) {
    			System.err.println("使用java8之前的版本/姓名 : " + entry.getKey() + " 分数 : " + entry.getValue());
    		}
    	
    		//java8版本
    		items.forEach((k,v)->{
    			System.err.println("使用java8循环 /姓名 : " +k + " 分数 : " + v);
    			});
    		
    		items.forEach((k,v)->{
    			if(k.equals("小文")){
    				System.out.println("hello "+k);
    			}
    		});
    		
    		System.out.println("------华丽的分割线-----");
    		
    		//操作List部分
    		List<User> itemsList = new ArrayList<>();
    		User user1 =CreateFactory.create(User::new);
    		user1.setId("1");
    		user1.setUserName("xw");
    		user1.setAge("12");
    		itemsList.add(user1);
    		User user2 =CreateFactory.create(User::new);
    		user2.setId("2");
    		user2.setUserName("xj");
    		user2.setAge("23");
    		itemsList.add(user2);
    		for(User item : itemsList){
    		    System.out.println(item.getId()+"-"+item.getUserName()+"-"+item.getAge());
    		}
    		
    		System.out.println("------华丽的分割线-----");
    		
    		//java8版本
    		itemsList.forEach(item->{
    			System.out.println(item.getUserName());
    		});
    		
    		//条件过滤
    		itemsList.forEach(item->{
    			String userName = item.getUserName();
    			if(userName.equals("xj")){
    				System.out.println("大家好我是"+userName);
    			}
    		});
    		
    		//方法的引用
    		itemsList.forEach(System.out::println);
    		
    		//stream and filter
    		itemsList.stream().filter(itemuser->itemuser.getUserName().equals("xj")).forEach(item ->{
    			System.out.println("...........stream........");
    			System.err.println(item.getUserName());
    		});
    	}
    }

**附带User**

package com.ven.java8.foreach;
    
    public class User {
    
    	private String id;
    	
    	private String userName;
    	
    	private String age;
    
    	public String getId() {
    		return id;
    	}
    
    	public void setId(String id) {
    		this.id = id;
    	}
    
    	public String getUserName() {
    		return userName;
    	}
    
    	public void setUserName(String userName) {
    		this.userName = userName;
    	}
    
    	public String getAge() {
    		return age;
    	}
    
    	public void setAge(String age) {
    		this.age = age;
    	}
    	
    	
    }