java中Map循环的几种方式

爱被打了一巴掌 2022-05-19 01:44 201阅读 0赞

package com.xhx.collection;
    
    import org.junit.Test;
    
    import java.util.HashMap;
    import java.util.Iterator;
    import java.util.Map;
    
    /**
     * xuhaixing
     * 2018/7/15 19:59
     **/
    public class TestHashMapApp {
    
    
        /**
         * 循环的几种方式
         */
        @Test
        public void testHashMap1(){
            Map<String,String> map = new HashMap<String, String>();
            map.put("a","aaa");
            map.put("b","bbb");
            map.put("c","ccc");
            map.put("d","ddd");
    
            //通过key    Set<T> key = map.keySet()
            for(String key:map.keySet()){
                System.out.println("key="+key+" value="+map.get(key));
            }
    
            //key和value都循环
            for(Map.Entry<String,String> entry : map.entrySet()){
                System.out.println("key="+entry.getKey()+" value="+entry.getValue());
            }
    
            //通过迭代器
            Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();
            while (iterator.hasNext()){
                Map.Entry<String, String> entry = iterator.next();
                System.out.println("key="+entry.getKey()+" value="+entry.getValue());
            }
    
            //只循环value
            for(String value : map.values()){
                System.out.println("value="+value);
            }
    
        }
    }

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