Java中“==”和equals的区别

Java中“==”和equals的区别

• “==”可以适用于基本数据类型和应用数据类型，equals()只能适用于引用数据类型
• 对于引用数据类型

  • “==”比较两个引用类型的地址值是否相同
    

  • equals()不重写的话，比较的也是两个引用类型的地址值是否相同；equals()重写的话，比较的也是两个引用类型的内容是否相同
    

public class test{
    public static void main(String[] args) {
        MyData mydata1 = new MyData(12, 5, 1984);
        MyData mydata2 = new MyData(12, 5, 1984);

        // == 和 equals() 的测试
        if (mydata1 == mydata2) {
            System.out.println("mydata1 == mydata2");
        }else {
            System.out.println("madata1 != mydata2");
        }

        if (mydata1.equals(mydata2)) {
            System.out.println("mydata1 equals mydata2");
        } else {
            System.out.println("mydata1 no equals mydata2");
        }
    }
}
class MyData{
    private int day;
    private int month;
    private int year;

    public MyData(int day, int month, int year) {
        this.day = day;
        this.month = month;
        this.year = year;
    }
    //重写equals()方法
    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj instanceof MyData) {
            MyData mydata = (MyData) obj;
            return this.day == mydata.day && this.month==mydata.month && this.year == mydata.year;
        }
        return false;
    }

    }
}

上述代码执行结果：

madata1 != mydata2
mydata1 equals mydata2