Question

I have one class and I want compare two objects of that class. Is there any method to
compare two user defined objects. I don’t want to do it manually.

public class NewClass {

    private String name;
    private String surnamename;
    private String address;

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

    public NewClass(String name, String surname, String address)
    {
        this.name = name;
        this.surnamename = surname;
        this.address = address;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSurnamename() {
        return surnamename;
    }
    public void setSurnamename(String surnamename) {
        this.surnamename = surnamename;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
}

I want to compare two objects of this class. how could I accomplish this?

NewClass newClass1 = new NewClass("kshitij", "solanki", "nadiad");      
NewClass newClass2 = new NewClass("kshitij", "solanki", "nadiad");

    String s1 = new String("kshitij");
    String s2 = new String("kshitij");

    NewClass s3 = new NewClass("kshitij");
    NewClass s4 = new NewClass("kshitij");

    System.out.println(s1.hashCode());
    System.out.println(s2.hashCode());

    System.out.println(s3.hashCode());
    System.out.println(s4.hashCode());

    System.out.println(newClass1 == newClass2);
    System.out.println(newClass1.toString() == newClass2.toString());
    System.out.println(newClass1.toString().equals(newClass2.toString()));

Answer 1

You want to implement equals and hashCode, e.g.

public boolean equals(final Object other) {
  if (other instanceof NewClass) {
    final NewClass _other = (NewClass) other;
    return name.equals(_other.name)
      && (surname == null && surname == _other.surname
        || surname.equals(_other.surname))
      && (address == null && address == _other.address
        || address.equals(_other.address));
  } else {
    return false;
  }
}

public int hashCode() {
  return name.hashCode() * 961
    + (surname == null ? 0 : surname.hashCode()) * 31
    + (address == null ? 0 : address.hashCode());
}

Now, you can compare NewClass instances by their semantics, e.g.

/* they are equal */
assert new NewClass("A", "B", "C").equals(new NewClass("A", "B", "C"));