以下代码显示如何实现equals()和hashCode()方法
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class Point { private int x; private int y; public Point(int x, int y) { this.x = x; this.y = y; } /* implement the equals() method */ public boolean equals(Object otherObject) { // Are the same? if (this == otherObject) { return true; } // Is otherObject a null reference? if (otherObject == null) { return false; } // Do they belong to the same class? if (this.getClass() != otherObject.getClass()) { return false; } // Get the reference of otherObject in a SmartPoint variable Point otherPoint = (Point) otherObject; // Do they have the same x and y co-ordinates boolean isSamePoint = (this.x == otherPoint.x && this.y == otherPoint.y); return isSamePoint; } /* * implement hashCode() method of the Object class, which is a requirement * when you implement equals() method */ public int hashCode() { return (this.x + this.y); }}public class Main { public static void main(String[] args) { Point pt1 = new Point(10, 10); Point pt2 = new Point(10, 10); Point pt3 = new Point(12, 19); Point pt4 = pt1; System.out.println("pt1 == pt1: " + (pt1 == pt1)); System.out.println("pt1.equals(pt1): " + pt1.equals(pt1)); System.out.println("pt1 == pt2: " + (pt1 == pt2)); System.out.println("pt1.equals(pt2): " + pt1.equals(pt2)); System.out.println("pt1 == pt3: " + (pt1 == pt3)); System.out.println("pt1.equals(pt3): " + pt1.equals(pt3)); System.out.println("pt1 == pt4: " + (pt1 == pt4)); System.out.println("pt1.equals(pt4): " + pt1.equals(pt4)); }} |
上面的代码生成以下结果。