Can someone help me with equals()?

4103375

Im new at Java so i dont understand too much. Im studing computer engineering and our teacher asked us to complete the followin code:

// Represents a rectangle

public class Rectangle {

// Initializes a new rectangle with the values passed by parameter .

// Throws IllegalArgumentException if a a negative value is passed to any of

// the dimensions .

public Rectangle ( int base , int height ) { }

// Copy constructor

public Rectangle ( Rectangle r ) { }

// Getters

public int getBase () { }

public int getHeight () { }

// Setters . Throw IllegalArgumentException if the parameters are negative .

public void setBase ( int base ) { }

public void setHeight ( int height ) { }

// Return true if the rectangle is a square

public boolean isSquare () { }

// Calculate the area of the rectangle .

public int area () { }

// Calculate the perimeter of the rectangle .

public int perimeter () { }

// Calculate the length of the diagonal

public double diagonal () { }

// Turn this rectangle 90 degrees ( changing base by height ).

public void turn () { } // Ensure that this rectangle is oriented horizontally ( the base is greater // or equal than the height ).

public void putHorizontal () { } // Ensure that this rectangle is oriented vertically ( the height is greater // or equal than the base ).

public void putVertical () { }

// Two rectangles are equal if the base and the height are the same . // It does not take into account if the rectangle is rotated .

public boolean equals ( Object obj ) { }

// It complies with the hashCode contract and is consistent with the equals .

public int hashCode () { } }

I made it to the followin point:

package e3;

   // Represents a rectangle

public class Rectangle {

    private int height;

    private int base;

// Initializes a new rectangle with the values passed by parameter .

// Throws IllegalArgumentException if a a negative value is passed to any of

// the dimensions .

public Rectangle ( int base , int height ) {

    if (base <= 0 || height <= 0) {

        throw new IllegalArgumentException();

        }

    this.base=base;

    this.height=height;

}

// Copy constructor

public Rectangle ( Rectangle r ) {

    this.base=r.base;

    this.height=r.height;

}

// Getters

public int getBase () {

return base;

}

public int getHeight () {

return height;

}

// Setters . Throw IllegalArgumentException if the parameters are negative .

public void setBase ( int base ) {

    if (base < 0) {

        throw new IllegalArgumentException();

        }

     this.base = base;

}

public void setHeight ( int height ) {

   

    if ( height < 0) {

        throw new IllegalArgumentException();

        }

    this.height = height;

}

// Return true if the rectangle is a square

public boolean isSquare () {

    if(height==base){

    return true;

    }

    return false;

}

// Calculate the area of the rectangle .

public int area () {

    int area;

    area = base*height;

    return area;

   

}

// Calculate the perimeter of the rectangle .

public int perimeter () {

    int perimeter;

    perimeter =(2*height)+(2*base);

    return perimeter;

}

// Calculate the length of the diagonal

public double diagonal () {

    int a;

    double diagonal;

    a=((base*base)+(height*height));

    diagonal = Math.sqrt(a);

    return diagonal;

}

// Turn this rectangle 90 degrees ( changing base by height ).

public void turn () {

    int aux;

    aux=base;

    base=height;

    height=aux;  

}

// Ensure that this rectangle is oriented horizontally ( the base is greater

// or equal than the height ).

public void putHorizontal () {

    if (base<height){

        int aux;

        aux=base;

        base=height;

        height=aux;

    }

}

// Ensure that this rectangle is oriented vertically ( the height is greater

// or equal than the base ).

public void putVertical () {

    if (height<base){

        int aux;

        aux=base;

        base=height;

        height=aux;

    }

}

// Two rectangles are equal if the base and the height are the same .

// It does not take into account if the rectangle is rotated .

@Override

public boolean equals ( Object obj ) {

Rectangle r=(Rectangle)obj;

return r.getBase().equals(this.getBase());

  

}

// It complies with the hashCode contract and is consistent with the equals .

public int hashCode () {

    return 0;

}

}

But i cannot understand the behaviour of the method equals() so i dont know how to continue. Can anyone help me? thank you.

rpc1

Hello!

At first you have to understand primitive types and it equality

At second there are plenty information about equals and hashCode (for example https://www.baeldung.com/java-equals-hashcode-contracts )

There is a hint from teacher:

// Two rectangles are equal if the base and the height are the same .

// It does not take into account if the rectangle is rotated .

You have to compare base and height of the rectangles, but at first you need to check that object is Rectangle

if (obj instanceof Rectangle)  {

     do something

} else {

     //obj is not Rectangle

     return false;

}