How to compare 2 boolean objects in Java

Question

I am trying to compare if two boolean values have the same logic value, but the code works only if I compare the same object,for the following code the output will be false and I don't understand why:

public class Logic {
    private boolean bo;
    public Logic(boolean bo) {
        this.bo=bo;
    }

    public boolean equals(Object obj) {
        if (this==obj)
            return true;
        else
            return false;
    }
    public static void main(String[] args) {
        Logic l1,l2;
        l1=new Logic(true);
        l2=new Logic (true);
        System.out.println(l1.equals(l2));

    }

}

Answer 1

You are comparing the objects not the attributes in your equals method. The right way would be:

public boolean equals(Logic obj) {
     return this.bo==obj.bo;
}

Answer 2

you can to use this

// compare() method of Boolean class

class GeeksforGeeks {

// Driver method 
public static void main(String[] args) 
{ 

    // first value 
    boolean a = true; 

    // second value 
    boolean b = true; 

    // compare method 
    System.out.println(a + " comparing with " + b 
                       + " = " + Boolean.compare(a, b)); 
} 

}

or check this link enter link description here

Answer 3

1. When you create the object by using new, as an example l1 would have a reference address in stack which is different object in the heap than l2.

2. You should not compare Object like that if you need Boxed Object like Ingeter, Boolean and etc. Right approach to do that unbox it, like below:

   Boolean b1 =new.., Boolean b2=new...; boolean bb1=b1; boolean bb2=b2; Now compare between bb1 and bb2;

Answer 4

As you know new objects are always created in heap space and the references to these objects are stored in stack memory. When you compare two objects using == it checks if their reference are point to the same object or not? It doesn't check objects content. Using your implementation of equal method (comparing object using == ), the output of running:

    public static void main(String[] args) {
        Logic l1, l2, l3;
        l1 = new Logic(true);
        l2 = new Logic(true);
        l3 = l1;
        System.out.println(l1.equals(l2));
        System.out.println(l1.equals(l3));
    }

would be:

false
true

Because l1 and l2 point to different objects but l1 and l3 point to a same object in heap. We should override equals method so that it compares equality of contents. According to the Java Language Specification, there is a contract between equals(Object) and hashCode():

If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

With these in mind we can override equals(Object obj) and hashCode() like this:

  @Override
  public int hashCode() {
    return Boolean.hashCode(bo);
  }

  @Override
  public boolean equals(Object obj) {
    if (obj == null) {
      return false;
    }
    if (this.getClass() == obj.getClass()) {
      return bo == ((Logic) obj).boValue();
    }
    return false;
  }

  private boolean boValue() {
    return bo;
  }