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MapTest.java
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75 lines (58 loc) · 1.83 KB
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package map;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import org.junit.Test;
import java.util.*;
public class MapTest {
/**
* map 赋值到list属于引用传递，不可用clear清除对象信息
*/
@Test
public void mapClearTest(){
Map<String,String> map1 = new HashMap();
List<Map> list = new ArrayList<>();
map1.put("name","bf");
map1.put("age","23");
map1.put("phone","110");
list.add(map1);
// [{phone=110, name=bf, age=23}]
System.out.println(list.toString());
map1.put("age","22");
System.out.println(list.toString());
map1.clear();
// [{}]
System.out.println(list.toString());
}
@Test
public void JSONObjeactClearTest(){
JSONObject map1 = new JSONObject();
JSONArray l = new JSONArray();
map1.put("name","bf");
map1.put("age","23");
map1.put("phone","110");
l.add(map1);
// [{"phone":"110","name":"bf","age":"23"}]
System.out.println(JSONArray.toJSONString(l));
map1.clear();
// [{}]
System.out.println(JSONArray.toJSONString(l));
}
/**
* 证明方法调用才会出现判断是否为空
*/
@Test
public void mapIsNullTest(){
Map<String,Object> map = new HashMap();
map.put("name","iceflow");
map.put("age",22);
String name = map.get("name").toString();
System.out.println(name);
// actual map,get("wife") is null
Object wife = map.get("wife");
// 这里会发生 java.lang.NullPointerException
System.out.println(wife.toString());
// 这里会发生 java.lang.NullPointerException
String phone = map.get("phone").toString();
System.out.println(phone);
}
}