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java
2 months ago
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// Online Java Compiler
// Use this editor to write, compile and run your Java code online
import java.util.HashMap;

class A {
    public int a;
    
    public A(int value) {
        this.a = value;
    }
    
    public boolean equals(Object other) {
        A other_a = (A)other;
        
        return this.a == other_a.a;
    }
    
    public int hashCode() {
        return this.a;
    }
    
    public String toString() {
        return "id:" + String.valueOf(System.identityHashCode(this)) + " a:" + String.valueOf(this.a);
    }
}

class HelloWorld {
    public static void main(String[] args) {
        A a = new A(1);
        A b = new A(2);
        
        HashMap<A, Integer> d = new HashMap<A, Integer>();
        
        d.put(a, 1);
        d.put(b, 2);
        
        System.out.println(a.toString());
        System.out.println(b.toString());
        System.out.println("eq " + a.equals(b));
        System.out.println("hash " + (a.hashCode() == b.hashCode()));
        
        System.out.println(d.toString());
        
        for(A key: d.keySet()) {
            if (key.a == 1) {
                key.a = 2;
            }
        }
        
        System.out.println(a.toString());
        System.out.println(b.toString());
        System.out.println("eq " + a.equals(b));
        System.out.println("hash " + (a.hashCode() == b.hashCode()));
        
        System.out.println(d.toString());
        
        HashMap<A, Integer> new_d = new HashMap<A, Integer>();
        
        new_d.put(a, 1);
        new_d.put(b, 2);
        
        System.out.println(new_d.toString());
    }
}
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