equals，hashCode，compareTo的重写

最新推荐文章于 2023-10-24 21:39:35 发布

lxhlovemy

最新推荐文章于 2023-10-24 21:39:35 发布

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CC 4.0 BY-SA版权

文章标签： equals string integer object class import

本文链接：https://blog.youkuaiyun.com/lxhlovemy/article/details/6508011

本文展示了一个使用Java集合框架的例子，特别是HashSet，并演示了如何为自定义类实现equals和hashCode方法以确保正确的行为。

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import java.util.*;

public class BasicContainer {
    public static void main(String[] args) {
        Collection c = new HashSet();                          //父类引用指向子类对象~ 灵活方便~！
        c.add("hello");
        c.add(new Name("f1","l1"));
        c.add(new Integer(100));
        c.remove("hello");
        c.remove(new Integer(100));
        System.out.println
                  (c.remove(new Name("f1","l1")));
        System.out.println(c);
    }

}

class Name implements Comparable {
    private String firstName,lastName;
    public Name(String firstName, String lastName) {
        this.firstName = firstName; this.lastName = lastName;
    }
    public String getFirstName() { return firstName;   }
    public String getLastName() {   return lastName;   }
    public String toString() { return firstName + " " + lastName; }

    public boolean equals(Object obj) {                                     //重写equals的时候重写hashcode；
     if (obj instanceof Name) {
         Name name = (Name) obj;
         return (firstName.equals(name.firstName))
             && (lastName.equals(name.lastName));
     }
     return super.equals(obj);
  }
  public int hashCode() {
      return firstName.hashCode();
  }



  public int compareTo(Object o) {
        Name n = (Name)o;
        int lastCmp =
            lastName.compareTo(n.lastName);
        return
             (lastCmp!=0 ? lastCmp :
              firstName.compareTo(n.firstName));
    }

}