JAVA小练习126——增强for循环的练习

清疚 2022-01-15 14:47 229阅读 0赞

import java.util.HashSet;
    import java.util.Iterator;
    import java.util.Map.Entry;
    import java.util.Set;
    import java.util.TreeMap;
    
    public class Demo126 {
    	
    	public static void main(String[] args) {
    		HashSet<String>  set = new HashSet<String>();
    		set.add("张三");
    		set.add("李四");
    		set.add("王五");
    		
    		System.out.println("===========迭代器的遍历方式===========");
    		
    		 Iterator<String> it = set.iterator();
    		 //使用迭代器
    		 while(it.hasNext()){ String
    		 item = it.next(); 
    		 System.out.print(item +","); //it.remove(); }
    		 }
    		 
    		for(String item : set){  //遍历出来的每个元素都会交给item变量。
    			System.out.print(item+",");
    		
    		}
    		int[] arr = {19,17,18,30};
    		
    		//普通的for循环遍历
    		for(int i = 0 ; i<arr.length ; i++){
    			System.out.print(arr[i]+",");
    		}
    		
    		
    		//增强for循环
    		for(int item :arr){
    			System.out.print(item+",");
    		}
    		
    		
    		/*//在控制台打印5句hello world
    		for(int i = 0 ; i<5; i++){
    			System.out.println("hello world");
    			*/
    			
    			int[] arr2 = new int[5];
    			
    			for(int item:arr2){
    				System.out.println("hello world");
    		}
    		
    			
    			 TreeMap<Integer, String> tree = new TreeMap<Integer, String>(); 
    			 
    			 tree.put(110,"张三"); 
    			 tree.put(109, "李四"); 
    			 tree.put(120, "王五");
    			 tree.put(115, "赵六");
    			  
    			 //使用增强for循环遍历map集合
    			 Set<Entry<Integer, String>> entryes = tree.entrySet();
    			 for(Entry<Integer, String> entry : entryes){
    			 System.out.println("键："+entry.getKey()+" 值："+ entry.getValue()); }
    			 
    		
    		
    		
    		
    		
    	
    	}
    
    }