Overriding toString() method in java

Object class toString() method will call internally by default whenever we print object reference even though object contains content.

public class StudentRecord {

       public static void main(String[] args) {

              Student s1=new Student(10);

              System.out.println(s1); //output : Student@1db9742           

       }

}

class Student{

       int id;

       Student(int id){

              this.id=id;

       }     

}

We got the output:  Student@1db9742 even we passed id=10

Whenever object class toString() called, internally it call hashCode()

Internal code of toString()

  

  public String toString()

  {

    return getClass().getName() + "@" + Integer.toHexString(hashCode());

  }

toString() return output as

Class name @ hexadecimal hashcode

If we override toString() method in our class then toString() method don’t call hashcode() method.

public class StudentRecord {

       public static void main(String[] args) {

              Student s1=new Student(10);

              System.out.println(s1); //output : Student id : 10           

       }

}

class Student{

       int id;

       Student(int id){

              this.id=id;

       }

       @Override

       public String toString() {       

              return "Student id : "+id;

       }

}

Whenever we override toString() method in our class it returns exact content of object (meaningful representation).

Above program gives output as:  Student id : 10

Note: String class overridden toString() method and it give meaningful representation by default

Example:

public class Test {

  public static void main(String[] args) {

        String s1=new String("hello world");   

        System.out.println(s1);// hello world

 }

}

In this program we doesn’t override toString() method any where even though it given exact output because we taken String class.