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Tags
#bloch-effective-java-2ed #java
Question

What are the consequences of implementing equals() method like this (using getClass() instead of using instanceof)?


public class Point {
     @Override public boolean equals(Object o) {
     if (o == null || o.getClass() != getClass())
         return false;
     Point p = (Point) o;
     return p.x == x && p.y == y;
 }
}
Answer
Liskov substitution principle is violated. For example, we cannot mix Points and objects of any subclass of Point in collections, because Points and objects of any subclass of Point will never be equal, even if subclassing is NOT adding any value field.

Tags
#bloch-effective-java-2ed #java
Question

What are the consequences of implementing equals() method like this (using getClass() instead of using instanceof)?


public class Point {
     @Override public boolean equals(Object o) {
     if (o == null || o.getClass() != getClass())
         return false;
     Point p = (Point) o;
     return p.x == x && p.y == y;
 }
}
Answer
?

Tags
#bloch-effective-java-2ed #java
Question

What are the consequences of implementing equals() method like this (using getClass() instead of using instanceof)?


public class Point {
     @Override public boolean equals(Object o) {
     if (o == null || o.getClass() != getClass())
         return false;
     Point p = (Point) o;
     return p.x == x && p.y == y;
 }
}
Answer
Liskov substitution principle is violated. For example, we cannot mix Points and objects of any subclass of Point in collections, because Points and objects of any subclass of Point will never be equal, even if subclassing is NOT adding any value field.
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pdf

owner: piotr.wasik - (no access) - Effective Java (Joshua Bloch), 2ed, p39

Summary

statusnot learnedmeasured difficulty37% [default]last interval [days]               
repetition number in this series0memorised on               scheduled repetition               
scheduled repetition interval               last repetition or drill

Details

No repetitions

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