Java - Character.Subset toString() Method

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The Java Character.Subset toString() method retrieves the name of a given subset.

But what is the name of a subset and how is it defined? Let us learn below −

To instantiate a subset object, we will be making use of the inheritance concept in Java. The Character.Subset class is extended or inherited from any super class, say CharacterSubsetDemo. The constructor of the CharacterSubsetDemo class is invoked when the object of this class is instantiated using a String. This String is treated as the name of the subset object.

Note − This method uses the inheritance concept to create a Subset object as the constructor in the Character.Subset class has protected access. Therefore, Character.Subset class is extended from another public class whose constructor uses super() method to invoke the Object class that creates an object.

Syntax

Following is the syntax for Java Character.Subset toString() method

public final String toString()

Parameters

This method does not accept any parameters.

Return Value

This method returns a string representation of the object.

Example

The following example shows the usage of Java Character.Subset toString() method. To create an object, the constructor of the CharacterSubsetDemo class invokes the constructor of the Object class with the given String argument using the super() method. Hence, a new object is instantiated each time the constructor is called. The method Java Character.Subset.toString() is then called on these objects to obtain the string representation of them each.

package com.tutorialspoint;
import java.lang.*;
public class CharacterSubsetDemo extends Character.Subset {
  
   // constructor of super class
   CharacterSubsetDemo(String s) {
      super(s); 
   }
   public static void main(String[] args) {
      CharacterSubsetDemo str1 = new CharacterSubsetDemo("admin");
      CharacterSubsetDemo str2 = new CharacterSubsetDemo("webmaster");
      CharacterSubsetDemo str3 = new CharacterSubsetDemo("administrator");

      // returns a string representation of the object
      System.out.println("String1 = " + str1.toString());
      System.out.println("String2 = " + str2.toString());
      System.out.println("String3 = " + str3.toString());
   }
}

Output

Let us compile and run the above program, this will produce the following result −

String1 = admin
String2 = webmaster
String3 = administrator

Example

The string name can be of any character, even symbols; therefore, in this example we will see the usage of the Java Character.Subset toString() method on Subset object that is instantiated using a string containing symbol characters −

import java.lang.*;
public class CharacterSubsetDemo extends Character.Subset {
   CharacterSubsetDemo(String s) {
      super(s); //invokes the immediate super class: object 
   }
   public static void main(String[] args) {
      CharacterSubsetDemo str = new CharacterSubsetDemo("*@&^#($");
      System.out.println("String name = " + str.toString());
   }
}

Output

Let us compile and run the program given, so the output will be achieved as follows −

String name = *@&^#($

Example

We will see another example which instantiates a Subset object using digits as string name characters and see how the toString() method works −

import java.lang.*;
public class CharacterSubsetDemo extends Character.Subset {
   CharacterSubsetDemo(String s) {
      super(s); //invokes the immediate super class: object 
   }
   public static void main(String[] args) {
      CharacterSubsetDemo str = new CharacterSubsetDemo("121393");
      System.out.println("String name = " + str.toString());
   }
}

Output

The output is obtained after compiling and executing the program given above −

String name = 121393

Example

In this example, if the string name used to declare and initialize an object is null, the program is executed as follows after invoking the toString() method −

import java.lang.*;
public class CharacterSubsetDemo extends Character.Subset {
  
   // constructor of super class
   CharacterSubsetDemo(String s) {
      super(s); //invokes the immediate super class: object 
   }
   public static void main(String[] args) {
      CharacterSubsetDemo str = new CharacterSubsetDemo(null); //no string name given

      // returns a string representation of the object
      System.out.println("String name = " + str.toString());
   }
}

Exception

A NullPointerException is thrown as the string name is given null; hence, the output will be displayed as follows −

Exception in thread "main" java.lang.NullPointerException: nameat java.lang.Character$Subset.<init>(Character.java:615)
at CharacterSubsetDemo.<init>(CharacterSubsetDemo.java:7)
at CharacterSubsetDemo.main(CharacterSubsetDemo.java:12)