Understanding toString() method

by Online Tutorials Library July 22, 2022

Java toString() Method

If you want to represent any object as a string, toString() method comes into existence.

The toString() method returns the String representation of the object.

If you print any object, Java compiler internally invokes the toString() method on the object. So overriding the toString() method, returns the desired output, it can be the state of an object etc. depending on your implementation.

Advantage of Java toString() method

By overriding the toString() method of the Object class, we can return values of the object, so we don’t need to write much code.

Understanding problem without toString() method

Let’s see the simple code that prints reference.

Student.java

  class Student{   int rollno;   String name;   String city;     Student(int rollno, String name, String city){   this.rollno=rollno;   this.name=name;   this.city=city;   }     public static void main(String args[]){     Student s1=new Student(101,”Raj”,”lucknow”);     Student s2=new Student(102,”Vijay”,”ghaziabad”);          System.out.println(s1);//compiler writes here s1.toString()     System.out.println(s2);//compiler writes here s2.toString()   }  }    

Output:

[email protected]  [email protected]

As you can see in the above example, printing s1 and s2 prints the hashcode values of the objects but I want to print the values of these objects. Since Java compiler internally calls toString() method, overriding this method will return the specified values. Let’s understand it with the example given below:

Example of Java toString() method

Let’s see an example of toString() method.

Student.java

  class Student{   int rollno;   String name;   String city;     Student(int rollno, String name, String city){   this.rollno=rollno;   this.name=name;   this.city=city;   }      public String toString(){//overriding the toString() method    return rollno+” “+name+” “+city;   }   public static void main(String args[]){     Student s1=new Student(101,”Raj”,”lucknow”);     Student s2=new Student(102,”Vijay”,”ghaziabad”);          System.out.println(s1);//compiler writes here s1.toString()     System.out.println(s2);//compiler writes here s2.toString()   }  }    

Output:

101 Raj lucknow  102 Vijay ghaziabad

In the above program, Java compiler internally calls toString() method, overriding this method will return the specified values of s1 and s2 objects of Student class.

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