Difference between throw and throws in Java?

java throw throws
user3527594 picture user3527594 · Sep 2, 2014 · Viewed 70.1k times · Source

Can any one clearly state the difference between throw and throws in Java exception handling with an example? I have tried googling but couldn't arrive at a conclusion. Pls help

Answer

Nirav Prajapati picture Nirav Prajapati · Sep 2, 2014

  1. throws clause is used to declare an exception and throw keyword is used to throw an exception explicitly.

  2. If we see syntax wise then throw is followed by an instance variable and throws is followed by exception class names.

  3. The keyword throw is used inside method body to invoke an exception and throws clause is used in method declaration (signature).

For example

throw 

throw new Exception("You have some exception")
throw new IOException("Connection failed!!")

throws

public int myMethod() throws IOException, ArithmeticException, NullPointerException {}

  1. You cannot declare multiple exceptions with throw. You can declare multiple exception e.g. public void method()throws IOException,SQLException.

  2. checked exceptions can not be propagated with throw only because it is explicitly used to throw an particular exception. checked exception can be propagated with throws.

Exception propagation: An exception propagates from method to method, up the call stack, until it's caught. So if a() calls b(), which calls c(), which calls d(), and if d() throws an exception, the exception will propagate from d to c to b to a, unless one of these methods catches the exception. what is exception propagation?

Related questions

Is there a throws keyword in C# like in Java?

Possible Duplicate: how to use Java-style throws keyword in C#? i have a function where an exception occurs say for example private void functionName() throws Exception { // some code that might throw an exception } thanks!

Read More
Exception handling : throw, throws and Throwable

Can any of you explain what the differences are between throw, throws and Throwable and when to use which?

Read More
Difference between Throws in method signature and Throw Statements in Java

I am trying to make it clear of the difference between Throws in method signature and Throw Statements in Java. Throws in method signature is as following: public void aMethod() throws IOException{ FileReader f = new FileReader("notExist.txt"); } Throw Statements …

Read More