如何检查价值平等? [英] How to check for value equality?
问题描述
我是Java初学者,所以请忍受这个。
I'm a Java-beginner, so please bear with this one.
我有一个课程:
class Point {
public int x;
public int y;
public Point (int x, int y) {
this.x = x;
this.y = y;
}
}
我创建了两个实例:
Point a = new Point(1, 1);
Point b = new Point(1, 1);
我想检查这两个点是否在同一个地方。显而易见的是,如果(a == b){...}
,则不起作用,因为这似乎是是对象等于?一种测试,这不是我想要的。
I want to check if these two points are at the same place. The obvious way, if (a == b) { ... }
, does not work since this seems to be an "are the objects equal?" kind of test, which is not what I want.
我能做 if((ax == bx)&&(ay = =))){...}
,但是这个解决方案感觉不太好。
I can do if ( (a.x == b.x) && (a.y == b.y) ) { ... }
, but that solution does not feel good.
如何获取两个Point-objects并测试它们是否平等,以优雅的方式协调?
How can I take two Point-objects and test them for equality, coordinate wise, in an elegant way?
推荐答案
标准协议是实现 等于()
方法:
The standard protocol is to implement the equals()
method:
class Point {
...
@Override
public boolean equals(Object obj) {
if (!(obj instanceof Point)) return false;
Point rhs = (Point)obj;
return x == rhs.x && y == rhs.y;
}
然后你可以使用 a.equals(b)
。
请注意,一旦完成此操作,您还需要实现 hashCode()
方法。
Note that once you've done this, you also need to implement the hashCode()
method.
对于像你这样的课程,我经常使用 Apache Commons Lang 的< a href =http://commons.apache.org/lang/api-2.5/org/apache/commons/lang/builder/EqualsBuilder.html> EqualsBuilder
和 HashCodeBuilder
:
For classes like yours, I often use Apache Commons Lang's EqualsBuilder
and HashCodeBuilder
:
class Point {
...
@Override
public boolean equals(Object obj) {
return EqualsBuilder.reflectionEquals(this, obj);
}
@Override
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this);
}
}
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