Implementation method of java enhanced for loop

As shown below:

package cn.jdk.foreach;
 
import java.util.HashMap;
import java.util.Map;
 
public class ForEachTest {
    public static void main(String[] args) {
        int[] arr = {1,2,3};
        for(int a:arr){
            System.out.println(a+"\t");
        }
         
        System.out.println("==============================");
         
        Map<String,String> map = new HashMap<String,String>();
        map.put("1", "one");
        map.put("2", "two");
        map.put("3", "three");
        map.put("4", "four");
        map.put("5", "five");
         
        //map.keySet():循环遍历map的所有键，map.keySet()返回的是Set类型，而Set是可以被增强for遍历的。
        for(String key:map.keySet()){
            String value = map.get(key);//通过键获取对应的值
            System.out.println(key+"="+value);
        }
    }
 
}

<p>　增强for的优缺点</p><p>l  只能从头到尾的遍历数组或集合，而不能只遍历部分；</p><p>l  在遍历List或数组时，不能获取当前元素下标；</p><p>l  增强for使用便简单，这是它唯一的优点了；</p><p>l  增强for比使用迭代器方便一点！</p>

Map does not implement the Iterable interface, so you cannot directly use enhanced for to traverse it!

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