Discussion
What will be the output of the program?
import java.util.*;
public class Example19
{
static class Box { int v = 1; }
public static void main(String[] args)
{
List<Box> l = new ArrayList<Box>();
l.add(new Box());
System.out.println(l.contains(new Box()));
}
}
Answer: C
Box does not override equals, so it inherits identity comparison from Object and no two separately created boxes are ever equal. contains searches by equality and therefore returns false, even though the field values match. Overriding equals is what would make this true.
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