Overriding the equals() and hashCode() Methods in a Class - Java Object Oriented Design

Java examples for Object Oriented Design:Hash Code

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Description

Overriding the equals() and hashCode() Methods in a Class

Demo Code

class MyClass {/*from  w w  w.  j  a  v a 2 s  .c  o  m*/
  private String name;

  public MyClass(String name) {
    this.name = name;
  }

  /* Re-implement the equals() method */
  public boolean equals(Object otherObject) {
    // Are they the same?
    if (this == otherObject) {
      return true;
    }

    // Is otherObject a null reference?
    if (otherObject == null) {
      return false;
    }

    // Do they belong to the same class?
    if (this.getClass() != otherObject.getClass()) {
      return false;
    }

    // Get the reference of otherObject is a SmartCat variable
    MyClass otherCat = (MyClass) otherObject;

    // Do they have the same names
    boolean isSameName = (this.name == null ? otherCat.name == null : this.name
        .equals(otherCat.name));

    return isSameName;
  }

  /*
   * Re-implement the hashCode() method, which is a requirement when you
   * re-implement equals() method
   */
  public int hashCode() {
    return (this.name == null ? 0 : this.name.hashCode());
  }
}

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