目录
1.对Student类中重新实现quals方法(即对equals方法重写)
第一种: 用接口的方式实现,实现一个Comparable接口,并指定比较的类型
1.前置代码
1.学生类
class Student{ String name; int age; public Student(String name,int age){ this.name=name; this.age=age; }}
2.示例
Student student1 = new Student("fly",19); Student student2 = new Student("fly",19); System.out.println(student2==student1);
3.输出
输出: false ==//默认比较的是两个引用的地址
4.原因
原因:所有类默认继承于object,所以student1调用的是object的equals
equals的源码
public boolean equals(Object obj) { return (this == obj);}
obj:obj是参数
this:随调equals谁是this
return (this == obj);
等价于return students1 == students2
2.那么我们要怎么做呢?
1.对Student类中重新实现quals方法(即对equals方法重写)
//对equals方法进行重写(即自定义的equals方法) @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Student student = (Student) o; return age == student.age && Objects.equals(name, student.name); } //实现了比较时当年龄和名字相同的情况下,认为是同一个对象
2.完整代码如下:
class Student{ String name; int age; public Student(String name,int age){ this.name=name; this.age=age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Student student = (Student) o; return age == student.age && Objects.equals(name, student.name); }}
3.具体操作
在IDEA右键generate(快捷键:Alt+Insert),
再选择equals() and hashCode(),一路next就ok了
4.演示
1.示例
System.out.println(student1.equals(student2));
2.输出
输出:true
3.原因
当代码运行的时候,就会使用自定义的equals方法
实现了比较时当两个对象年龄和名字相同的情况下,会被认为是同一个对象
第一种: 用接口的方式实现,实现一个Comparable接口,并指定比较的类型
1.演示代码
class Student implements Comparable{ String name; int age; public Student(String name,int age){ this.name=name; this.age=age; } @Override public int compareTo(Student o) { return this.age-o.age; }}
2.示例
Student student1 = new Student("初一",19) Student student2 = new Student("初三",21); System.out.println(student1.equals(student2));//输出: -2 System.out.println(student1.compareTo(student2));//输出: 2 Student student3 = new Student("初五",19); System.out.println(student1.compareTo(student3));//输出: 0
3.代码输出结果
第二种: 使用比较器(博主推荐使用!!!)
1.演示代码
(1)名字比较器
class NameComparator implements Comparator { @Override public int compare(Student o1, Student o2) { return o1.name.compareTo(o2.name); }}
(2)年龄比较器
class AgeComparator implements Comparator { @Override public int compare(Student o1, Student o2) { return o1.age-(o2.age); }}
2.示例
Student student1 = new Student("初一",19); Student student2 = new Student("初三",21); Student student3 = new Student("初一",21); NameComparator nameComparator = new NameComparator(); int retName = nameComparator.compare(student1, student3); System.out.println(retName);//输出: 0 AgeComparator ageComparator = new AgeComparator(); int retAge=ageComparator.compare(student2,student3); System.out.println(retAge);//输出: 0 System.out.println(ageComparator.compare(student1, student3));//输出: -2 System.out.println(ageComparator.compare(student3, student1));//输出: 2
3.代码输出结果
来源地址:https://blog.csdn.net/m0_73740682/article/details/132413358