equals()方法练习

1：

package com.aff.equals;

public class TestOrder {
    public static void main(String[] args) {
        Order o1 = new Order(1001, "AA");
        Order o2 = new Order(1001, "AA");
        System.out.println(o1 == o2);// false
        System.out.println(o1.equals(o2));// false--->true  重写equals方法后
    }
}

class Order {
    private int orderId;
    private String orderName;

    public int getOrderId() {
        return orderId;
    }

    public void setOrderId(int orderId) {
        this.orderId = orderId;
    }

    public String getOrderName() {
        return orderName;
    }

    public void setOrderName(String orderName) {
        this.orderName = orderName;
    }

    public Order(int orderId, String orderName) {
        super();
        this.orderId = orderId;
        this.orderName = orderName;
    }

    //比较两个order对象的属性是否完全相同，相同的话返回true
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        } else if (obj instanceof Order) {
            Order o1 = (Order) obj;
            return this.orderId == o1.orderId && this.orderName.equals(o1.orderName);
        } else {
            return false;
        }
    }
}

输出结果：

false
true

2：

package com.aff.equals;

public class TestMyDate {
    public static void main(String[] args) {
        MyDate m1 = new MyDate(12, 3, 2012);
        MyDate m2 = new MyDate(12, 3, 2012);

        if (m1 == m2) {
            System.out.println("m1==m2");
        } else {
            System.out.println("m1!=m2");
        }
        // boolean java.lang.Object.equals(Object obj)
        // 调用的为Object里面的equals方法，需要重写equals方法
        if (m1.equals(m2)) {
            System.out.println("m1 is equals m2");
        } else {
            System.out.println("m1 is not  equal to m2");
        }
    }
}

class MyDate {
    private int day;
    private int month;
    private int year;

    public MyDate(int day, int month, int year) {
        super();
        this.day = day;
        this.month = month;
        this.year = year;
    }

    public int getDay() {
        return day;
    }

    public void setDay(int day) {
        this.day = day;
    }

    public int getMonth() {
        return month;
    }

    public void setMonth(int month) {
        this.month = month;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    //手动写的
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        } else if (obj instanceof MyDate) {
            MyDate m = (MyDate) obj;
            return this.day == m.day && this.month == m.month && this.year == m.year;
        } else {
            return false;
        }
    }
}

输出结果：

m1!=m2
m1 is equals m2