map put

public class test {
    static Map<String, Map<String, Integer>> mapB = new HashMap<String, Map<String, Integer>>();
    static Map<String, Integer> mapA = new HashMap<String, Integer>();

    public test() {
        mapA.put("a", 66);
    }
    public static void main(String[] args) {
        test t = new test();
        System.out.println(mapA.get("a"));
        t.tempA(mapA);
        mapB.put("m", mapA);
        mapA.put("a", 2);
        mapA.put("b", 3);
        System.out.println(mapA.get("a") + " --- " + mapA.get("b"));
        System.out.println(mapB.get("m").keySet() + " ------ " + mapB.get("m"));
        System.out.println(mapA.get("a") + " --- " + mapA.get("b"));

    }

    public void tempA(Map<String, Integer> mapC) {
        mapC.put("a", 6);
    }
}

运行结果：

66
2 --- 3
[a, b] ------ {a=2, b=3}
2 --- 3