Assert - JAVA

Assert in Java

Assert is a reserved keyword not a method. It checks if the condition after it is true the application continues successfully otherwise vice versa.


This program shows how to use Assert in Java.

Assert.java

import javax.swing.JOptionPane;

public class Assert {
 public static void main(String args[]){
  //Get input
  String numeric = JOptionPane.showInputDialog("Enter a numeric value: ");
  //Check if the input is correct?
  assert checkInput(numeric); //assert true allows application to continue successfully and assert false throws an exception.
  System.out.println("You did pass a numeric value");
 }

 private static boolean checkInput(String numeric) {
  try {
   Integer.parseInt(numeric);
   return true;
  } catch (Exception e) {
   return false;
  }

 }
}

Note: You must add '-ea' argument in the command before running it to enable assert, otherwise assert won't work.