» » Difference between throw and throws in java

throw keyword:
  • throw keyword used to throw user defined exceptions.(we can throw predefined exception too)
  • If we are having our own validations in our code we can use this throw keyword.
  • For Ex: BookNotFoundException, InvalidAgeException (user defined).

Program:
  1. package com.instanceofjava;
  2. public class MyExceptionThrow {
  3.  
  4.  public static void main(String a[]){
  5.  
  6.  try{
  7.  
  8. MyExceptionThrow thr = new MyExceptionThrow();
  9. System.out.println("length of INDU is "+thr.getStringSize("INDU"));
  10. System.out.println("length of SAIDESH is "+thr.getStringSize("SAIDSH"));
  11. System.out.println("length of null string is "+thr.getStringSize(null)); 
  12.  
  13.  }
  14. catch (Exception ex){
  15.   System.out.println("Exception message: "+ex.getMessage());  
  16.  }
  17.  }
  18.  
  19.  public int getStringSize(String str) throws Exception{
  20.  
  21.  if(str == null){
  22.    throw new Exception("String input is null");  
  23.  }
  24.  return str.length();
  25. }
  26.  
  27. }


Output
length of INDU is 4
length of SAIDESH is 5
Exception message: String input is null



 throws keyword:

  •  The functionality of throws keyword is only to explicitly to mention that the method is proven transfer un handled exceptions to the calling place.

Program:
  1. package com.instanceofjava;
  2. public class ExcpetionDemo {
  3.  
  4. public static void main(String agrs[]){
  5.  
  6. try
  7. {
  8. //statements
  9. }
  10. catch(Exception e)
  11. {
  12. System.out.println(e);
  13. }
  14. finally(){compulsorily executable statements
  15. }
  16. }
  17.  
  18. }

Instance Of Java

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