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public class Tiger { private String color; private String stripePattern; private int height;

@Override public boolean equals(Object object) { boolean result = false; if (object == null || object.getClass() != getClass()) { result = false; } else { Tiger tiger = (Tiger) object; if (this.color == tiger.getColor() && this.stripePattern == tiger.getStripePattern()) { result = true; } } return result; }

// just omitted null checks @Override public int hashCode() { int hash = 3; hash = 7 * hash + this.color.hashCode(); hash = 7 * hash + this.stripePattern.hashCode(); return hash; }

public static void main(String args[]) { Tiger bengalTiger1 = new Tiger("Yellow", "Dense", 3); Tiger bengalTiger2 = new Tiger("Yellow", "Dense", 2); Tiger siberianTiger = new Tiger("White", "Sparse", 4); System.out.println("bengalTiger1 and bengalTiger2: " + bengalTiger1.equals(bengalTiger2)); System.out.println("bengalTiger1 and siberianTiger: " + bengalTiger1.equals(siberianTiger));

public class Tiger {
 private String color;
 private String stripePattern;
 private int height;
 
 @Override
 public boolean equals(Object object) {
 boolean result = false;
 if (object == null || object.getClass() != getClass()) {
 result = false;
 } else {
 Tiger tiger = (Tiger) object;
 if (this.color == tiger.getColor()
 && this.stripePattern == tiger.getStripePattern()) {
 result = true;
 }
 }
 return result;
 }
 
 // just omitted null checks
 @Override
 public int hashCode() {
 int hash = 3;
 hash = 7 * hash + this.color.hashCode();
 hash = 7 * hash + this.stripePattern.hashCode();
 return hash;
 }
 
 public static void main(String args[]) {
 Tiger bengalTiger1 = new Tiger("Yellow", "Dense", 3);
 Tiger bengalTiger2 = new Tiger("Yellow", "Dense", 2);
 Tiger siberianTiger = new Tiger("White", "Sparse", 4);
 System.out.println("bengalTiger1 and bengalTiger2: "
 + bengalTiger1.equals(bengalTiger2));
 System.out.println("bengalTiger1 and siberianTiger: "
 + bengalTiger1.equals(siberianTiger));
 
 System.out.println("bengalTiger1 hashCode: " + bengalTiger1.hashCode());
System.out.println("bengalTiger2 hashCode: " + bengalTiger2.hashCode());
System.out.println("siberianTiger hashCode: "
 + siberianTiger.hashCode());
 }
 
 public String getColor() {
 return color;
 }
 
 public String getStripePattern() {
 return stripePattern;
 }
 
 public Tiger(String color, String stripePattern, int height) {
 this.color = color;
 this.stripePattern = stripePattern;
 this.height = height;
 
 }
}

}

public String getColor() { return color; }

public String getStripePattern() { return stripePattern; }

public Tiger(String color, String stripePattern, int height) { this.color = color; this.stripePattern = stripePattern; this.height = height;

} }

Example Code Output:

bengalTiger1 and bengalTiger2: true bengalTiger1 and siberianTiger: false bengalTiger1 hashCode: 1398212510 bengalTiger2 hashCode: 1398212510 siberianTiger hashCode: –1227465966

bengalTiger1 and bengalTiger2: true 
bengalTiger1 and siberianTiger: false 
bengalTiger1 hashCode: 1398212510 
bengalTiger2 hashCode: 1398212510 
siberianTiger hashCode: –1227465966

public class Tiger { private String color; private String stripePattern; private int height;

@Override public boolean equals(Object object) { boolean result = false; if (object == null || object.getClass() != getClass()) { result = false; } else { Tiger tiger = (Tiger) object; if (this.color == tiger.getColor() && this.stripePattern == tiger.getStripePattern()) { result = true; } } return result; }

// just omitted null checks @Override public int hashCode() { int hash = 3; hash = 7 * hash + this.color.hashCode(); hash = 7 * hash + this.stripePattern.hashCode(); return hash; }

public static void main(String args[]) { Tiger bengalTiger1 = new Tiger("Yellow", "Dense", 3); Tiger bengalTiger2 = new Tiger("Yellow", "Dense", 2); Tiger siberianTiger = new Tiger("White", "Sparse", 4); System.out.println("bengalTiger1 and bengalTiger2: " + bengalTiger1.equals(bengalTiger2)); System.out.println("bengalTiger1 and siberianTiger: " + bengalTiger1.equals(siberianTiger));

System.out.println("bengalTiger1 hashCode: " + bengalTiger1.hashCode());
System.out.println("bengalTiger2 hashCode: " + bengalTiger2.hashCode());
System.out.println("siberianTiger hashCode: "
 + siberianTiger.hashCode());

}

public String getColor() { return color; }

public String getStripePattern() { return stripePattern; }

public Tiger(String color, String stripePattern, int height) { this.color = color; this.stripePattern = stripePattern; this.height = height;

} }

Example Code Output:

bengalTiger1 and bengalTiger2: true bengalTiger1 and siberianTiger: false bengalTiger1 hashCode: 1398212510 bengalTiger2 hashCode: 1398212510 siberianTiger hashCode: –1227465966

public class Tiger {
 private String color;
 private String stripePattern;
 private int height;
 
 @Override
 public boolean equals(Object object) {
 boolean result = false;
 if (object == null || object.getClass() != getClass()) {
 result = false;
 } else {
 Tiger tiger = (Tiger) object;
 if (this.color == tiger.getColor()
 && this.stripePattern == tiger.getStripePattern()) {
 result = true;
 }
 }
 return result;
 }
 
 // just omitted null checks
 @Override
 public int hashCode() {
 int hash = 3;
 hash = 7 * hash + this.color.hashCode();
 hash = 7 * hash + this.stripePattern.hashCode();
 return hash;
 }
 
 public static void main(String args[]) {
 Tiger bengalTiger1 = new Tiger("Yellow", "Dense", 3);
 Tiger bengalTiger2 = new Tiger("Yellow", "Dense", 2);
 Tiger siberianTiger = new Tiger("White", "Sparse", 4);
 System.out.println("bengalTiger1 and bengalTiger2: "
 + bengalTiger1.equals(bengalTiger2));
 System.out.println("bengalTiger1 and siberianTiger: "
 + bengalTiger1.equals(siberianTiger));
 
 System.out.println("bengalTiger1 hashCode: " + bengalTiger1.hashCode());
System.out.println("bengalTiger2 hashCode: " + bengalTiger2.hashCode());
System.out.println("siberianTiger hashCode: "
 + siberianTiger.hashCode());
 }
 
 public String getColor() {
 return color;
 }
 
 public String getStripePattern() {
 return stripePattern;
 }
 
 public Tiger(String color, String stripePattern, int height) {
 this.color = color;
 this.stripePattern = stripePattern;
 this.height = height;
 
 }
}

Example Code Output:

bengalTiger1 and bengalTiger2: true 
bengalTiger1 and siberianTiger: false 
bengalTiger1 hashCode: 1398212510 
bengalTiger2 hashCode: 1398212510 
siberianTiger hashCode: –1227465966
Source Link
rohan kamat
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  • 5
  • 12

equals() method is used to determine the equality of two objects.

as int value of 10 is always equal to 10. But this equals() method is about equality of two objects. When we say object, it will have properties. To decide about equality those properties are considered. It is not necessary that all properties must be taken into account to determine the equality and with respect to the class definition and context it can be decided. Then the equals() method can be overridden.

we should always override hashCode() method whenever we override equals() method. If not, what will happen? If we use hashtables in our application, it will not behave as expected. As the hashCode is used in determining the equality of values stored, it will not return the right corresponding value for a key.

Default implementation given is hashCode() method in Object class uses the internal address of the object and converts it into integer and returns it.

public class Tiger { private String color; private String stripePattern; private int height;

@Override public boolean equals(Object object) { boolean result = false; if (object == null || object.getClass() != getClass()) { result = false; } else { Tiger tiger = (Tiger) object; if (this.color == tiger.getColor() && this.stripePattern == tiger.getStripePattern()) { result = true; } } return result; }

// just omitted null checks @Override public int hashCode() { int hash = 3; hash = 7 * hash + this.color.hashCode(); hash = 7 * hash + this.stripePattern.hashCode(); return hash; }

public static void main(String args[]) { Tiger bengalTiger1 = new Tiger("Yellow", "Dense", 3); Tiger bengalTiger2 = new Tiger("Yellow", "Dense", 2); Tiger siberianTiger = new Tiger("White", "Sparse", 4); System.out.println("bengalTiger1 and bengalTiger2: " + bengalTiger1.equals(bengalTiger2)); System.out.println("bengalTiger1 and siberianTiger: " + bengalTiger1.equals(siberianTiger));

System.out.println("bengalTiger1 hashCode: " + bengalTiger1.hashCode());
System.out.println("bengalTiger2 hashCode: " + bengalTiger2.hashCode());
System.out.println("siberianTiger hashCode: "
 + siberianTiger.hashCode());

}

public String getColor() { return color; }

public String getStripePattern() { return stripePattern; }

public Tiger(String color, String stripePattern, int height) { this.color = color; this.stripePattern = stripePattern; this.height = height;

} }

Example Code Output:

bengalTiger1 and bengalTiger2: true bengalTiger1 and siberianTiger: false bengalTiger1 hashCode: 1398212510 bengalTiger2 hashCode: 1398212510 siberianTiger hashCode: –1227465966

lang-java

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