Question

我创建了一个存储对象Person的hashmap，键是一个String（Person的电子邮件地址）。我试图使用密钥删除hashmap中的条目，但不确定为什么它不会删除它。什么地方出了错？我的代码和输出都包含在内。任何帮助表示赞赏！

import java.util.HashMap;
import java.util.Map;

public class TestHashMap {

    private Map <String, Person> personDB = new HashMap<String, Person>();

    // added main to test the code
    public static void main(String[] args) {

TestHashMap org = new TestHashMap() ;

      // add data to personDB
org.add(new Person("A", "Smith","1234567890","ASmith@atest.com"));
org.add(new Person("B", "Smith","1234567890", "BSmith@atest.com"));
org.add(new Person("C", "Walsh","1234567890","CWalsh@atest.com"));
org.add(new Person("D", "Glatt","1234567890","DGlatt@atest.com"));
org.add(new Person("E", "Cheong", "1234567890","ACheong@atest.com"));
org.add(new Person("F", "Walsh","0123456789","FWalsh@sg.com"));

      // remove an element from personDB
org.display("testing ......before remove");  // display all elements in personDB
org.remove("ACheong@atest.com");
org.display("after..................");   
    }

    public void add(Person p) {
    String key = p.getEmail();
    personDB.put(key, p);
    }

    public void remove(String mail) {
Object obj = personDB.remove(personDB.get(mail));   
System.out.println(obj + " deleted!");
    }
}

我的输出：

testing ......before remove("ECheong@atest.com")
ID:[ASmith@atest.com]
ID:[CWalsh@atest.com]
ID:[FWalsh@sg.com]
ID:[ECheong@atest.com]
ID:[DGlatt@atest.com]
ID:[BSmith@atest.com]
null deleted!
after..................
ID:[ASmith@atest.com]
ID:[CWalsh@atest.com]
ID:[FWalsh@sg.com]
ID:[ECheong@atest.com]
ID:[DGlatt@atest.com]
ID:[BSmith@atest.com]

Answer 1

Object obj = personDB.remove(personDB.get(mail));

应该是

Object obj = personDB.remove(mail);

remove的参数是key，而不是元素。

Answer 2

人是关键，而不是“ACheong@atest.com”

这应该有效：

Person p = new Person("E", "Cheong", "1234567890","ACheong@atest.com");
org.remove(p);

无法从散列图中删除元素

2 个答案: