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. }