map集合的4种循环遍历

直接上代码：

package linruozhuo;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class JavaJihe {

	public static void main(String[] args) {
		Map<String ,String > map1 = new HashMap<String ,String >();
		map1.put("1", "小米");
		map1.put("2", "小红");
		map1.put("3", "小明");
		map1.put("4", "小华");
		
		//通过键找值遍历（效率低）
		System.out.println("通过Map.keySet遍历key和value：");
		  for (String key : map1.keySet()) {
		   System.out.println("key= "+ key + " and value= " + map1.get(key));
		  }
		  
		  
		// Iterator遍历
		System.out.println("通过Iterator遍历key和value：");
		Iterator<Map.Entry<String,String >> entries = map1.entrySet().iterator();
		  
		while (entries.hasNext()) {  
			  
			Map.Entry<String,String > entry = entries.next();  
		  
		    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());  
		}  
		
		
		//foreach分别遍历key和value
		System.out.println("foreach分别遍历key和value：");
		for (String key : map1.keySet()) {
			System.out.println("key= "+ key);
		}
		  
		for (String value : map1.values()) {
			System.out.println("value= "+ value);
		}  
		  
		//for循环
		System.out.println("for遍历key和value：");
		for (int i = 1; i <= map1.size(); i++) {
			String key = i+"";
			 System.out.println("key= "+ (i) + " and value= " + map1.get(key));
		}  
	  
		  
	}

}