例子一
public class Test1 {
public static void main(String[] args) {
Map map = new HashMap();
List violateList = new ArrayList();
map.put("violateList", violateList);
System.out.println(map);
violateList = getList();
System.out.println(violateList);
System.out.println(map);
/**
* 输出：
* {violateList=[]}
* [a, b, c, d]
* {violateList=[]}
*
* 原因：map的key指向violateList变量，本质是指向了violateList变量对应的对象体；
* violateList指向其他对象体时，不影响map的； 例子二可以证明
*/
}
public static List getList() {
List list = new ArrayList();
list.add("a");
list.add("b");
list.add("c");
list.add("d");
return list;
}
}
例子二
package test2016;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Test2 {
public static void main(String[] args) {
Map map = new HashMap();
List violateList = new ArrayList();
map.put("violateList", violateList);
System.out.println(map);
violateList.add("1");
violateList.add("2");
violateList.add("3");
violateList.add("4");
System.out.println(violateList);
System.out.println(map);
/**
* 输出：
* {violateList=[]}
* [1, 2, 3, 4]
* {violateList=[1, 2, 3, 4]}
*/
}
}
