Overriding Methods

AP Computer Science A· difficulty 4/5

public class Box {
    private int v;
    public Box(int x) { v = x; }
    public boolean equals(Object o) {
        if (!(o instanceof Box)) return false;
        return v == ((Box) o).v;
    }
}
// Usage:
Box b = new Box(3);
System.out.print(b.equals(null));

What is printed?

A
$false$
check_circle
B
$true$
C
$NullPointerException$
D
$Compile error$

Explanation

null instanceof anything is false, so the early return triggers and equals returns false. This is the safe pattern for handling null.

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