Here’s an example:

Code For Balance Class--------------------------------------------------------------------------------//  Demo class for User-Defined Exceptions To Ensure The//  Validity of Data Contained In A Classimport java.io.*;public class Balance{   int bal;   public Balance(){   }   public void setBalance( int amt ){      this.bal = amt;   }   public void withdraw( int amt )    throws NoSufficientFundException   {      if (bal >= amt) {         bal = bal - amt;      }      else  {         throw new NoSufficientFundException("Balance is less than what uexpect..some errormessage..");      }   }   public void getBalance()   {       return bal;   }}--------------------------------------------------------------------------------Code For NoSufficientFundException--------------------------------------------------------------------------------//  Exception Class For No Sufficient Fund(userdefined one)public class NoSufficientFundException extends Exception{    String strValue;	public PositionException( String value) {         this.strValue = value;	}	public String toString() {	   return "Exception occurred.. " + strValue;        }}--------------------------------------------------------------------------------Code For ( Test)Main Program--------------------------------------------------------------------------------// Test Program For Class Balance// Dealing With The Exceptions That It Throwsimport java.io.*;public class TestBalance{   static public void main( String[] args ) {      Balance obj = new Balance();      try {         obj.setBalance(100);         //some code....         obj.withdraw(150); //here the amount we specified is greater thanthe actual balance         obj.getBalance();      }      catch( NoSufficientFundException e )  {	     System.out.println(e);      } //end of catch   } //end of main}//end of TestBalance