"assert" keyword in Java

The assert keyword is used in assert statement which is a feature of the Java programming language since Java 1.4. Assertion enables developers to test assumptions in their programs as a way to defect and fix bugs.

Syntax of assert statement:-

(short version):

assert expression1;

 or (full version):

assert expression1 : expression2;

• expression1 must be a boolean expression.
• expression2 must return a value (must not return void).

By default,assertion is disabled at runtime to enable assertion,specify the switch -ea or 

-enableassertions  at command line of java program.for example to enable assertion for the program IsTest

                                                 

                                                       java -enableassertions IsTest 

or this for short

                                                              java -ea IsTest

1. You can combine switches to say disbale assertions in single class but keep enabled for       all others.                         

                                 java -ea -da:com.geekanonymous.Foo

    

    the preceding command line tells the jvm keep the assertions enable in general and             disable it for class Foo.

2. You can enable the assertion or disable the assertion in the System class with the -esa         and -dsa flags.

3. if assertion statement is false then it will throw Assertion Error which you should never           handle.

class Exc15

{

static int n=5;

       static int sum()

      {

      return --n; 

      }

public static void main(String args[])

{

      for(int i=0;i<=10;i++)

      {

      int ans=sum();

      assert ans>0;

     //assert ans>0 :"negative number";//give more information

     System.out.println(ans);

      }

}

}