[英]overriding equals method in java but getting logical errors/unexpected results
In this program i was trying to compare the field value of two reference variable value by overriding equals method---- Here is the code---- 在此程序中,我试图通过覆盖等于方法比较两个参考变量值的字段值----这是代码----
public class D {
int i,j;
D(int i,int j)
{
this.i=i;
this.j=j;
}
public boolean equals(Object f)
{
boolean s= (this.i==((D)f).i);
boolean n= (this.j==((D)f).j);
return s==n;
}
}
public class run02 {
public static void main(String[] args){
D d=new D(4,5);
D d1=new D(6,7);
D d2=new D(8,10);
System.out.println(d.equals(d1));//comparing reference variable value
System.out.println(d1.equals(d2));//comparing reference variable value
System.out.println(d);//printing reference variable memory address
System.out.println((d==d1));//comparing reference variable memory address
}
}
Output-true//comparing reference variable value
true//comparing reference variable value
firstProg.e@g3h742//memory address
false//comparing reference variable memory address
When i was trying to create a method public boolean equals(int i, intj) without giving return value then java throws compilation error. 当我试图创建一个方法public boolean equals(int i,intj)而不给出返回值时,java抛出编译错误。
The problem lies in this line: 问题出在这一行:
return s==n;
Here, this will return true
if both s
and n
are false
. 在这里,如果
s
和n
均为false
,则返回true
。
You should use s && n
to return true
only if both s
and n
are true
. 你应该用
s && n
返回true
只有当两个s
和n
是true
。
When i was trying to create a method public boolean equals(int i, intj) without giving return value then java throws compilation error.
当我试图创建一个方法public boolean equals(int i,intj)而不给出返回值时,java抛出编译错误。
Yes it will give you a compilation error because you are trying to cheat compiler, as in the method signature you are promising the compiler that at the end you will give it a boolean but in the end you are giving it anything. 是的,它会给您带来编译错误,因为您正试图欺骗编译器,因为在方法签名中,您向编译器承诺,最后将给它一个布尔值,但最后却给它任何东西。 So, that's why the compiler is complaining.
因此,这就是编译器抱怨的原因。
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