Java语言中深入研究Java equals方法

public boolean equals(Object obj)
{
if (obj == null) return false;
if (!(obj instanceof FieldPosition))
return false;
FieldPosition other = (FieldPosition) obj;
if (attribute == null) {
if (other.attribute != null) {
return false;
}
}
else if (!attribute.equals(other.attribute)) {
return false;
}
return (beginIndex == other.beginIndex
&& endIndex == other.endIndex
&& field == other.field);
}

package debug
;import java.text.*;
public class Test {
public static void main(String[] args) {
FieldPosition fp = new FieldPosition(10);
FieldPosition fp1 = new MyTest(10);
System.out.println(fp.equals(fp1));
System.out.println(fp1.equals(fp));
}
}
class MyTest extends FieldPosition{
int x = 10;
public MyTest(int x){
super(x);
this.x = x;
}
public boolean equals(Object o){
if(o==null) return false;
if(!(o instanceof MyTest )) return false;
return ((MyTest)o).x == this.x;
}
}

System.out.println(fp.equals(fp1));打印true
System.out.println(fp1.equals(fp));打印flase