增强for循环遍历 数组,Collection,Map

增强for循环:数组,Collection,Map

public class Demo {
    public static void main(String[] args) {
        /*
         * 增强for循环:数组,Collection,Map
         * for(元素类型  变量:数组/Collection){
         *      循环体
         * }
         * 
         * 注意:对于Map要进行特殊的处理:要先转成对应的Set,才能使用增强for循环
         */

        //遍历数组
        int[] arr = {3,45,6,8,9};
        for (int i : arr) {
            System.out.println("数组:"+i);
        }

        //遍历Collection
        ArrayList list = new ArrayList<>();
        list.add("java");
        list.add("php");

        for (String string : list) {
            System.out.println("list:"+string);
        }

        //遍历Map
        TreeMap map = new TreeMap<>();
        map.put("01", "php");
        map.put("02", "php2");
        map.put("05", "php5");

        //先转成set
        Set set1 = map.keySet();
        for (String string : set1) {
            System.out.println(map.get(string));
        }
        //或者
        Set> set1 = map.entrySet();
        for (Map.Entry entry : set1) {
            System.out.println(entry.getKey()+"  "+entry.getValue());
        }
    }
}