In this tutorial you will learn about difference between throw and throws keywords in java with example.
When we run a java program which contains errors, programmers should handle errors by exception handling (using try, catch and finally blocks) or avoid (throw) it. Otherwise JVM will give error which causes the termination of the running program and loss of data that has been processed till that line of the program.
Throw and Throws are two keywords used in java syntax related to exception feature of Java and used when programmer wants to throw the errors without handling.
Now let’s see the differences between the throw and throws clause.
Difference between Throw and Throws in Java
| Throw | Throws | |
| 1. | throw clause or keyword is used in Java to throw an exception explicitly. | throws clause or keyword is used in Java to declare an exception. |
| 2. | We can use throw in any part of code. | We must use throws only at method declaration. |
| 3. | At a time we can throw only one exception using throw keyword.
Ex: throw new IOException(“File not found”); |
At a time we can declare multiple exceptions using throws keyword.
Ex: public void func() throws IOException, SQLException { //some code} |
| 4. | throw is followed by instance only. | throws is followed by class name. |
| 5. | We cannot propagated checked exception using throw only. | We can propagated checked exception using throws. |
Throw Example
Example to explain the use of throw clause for throwing the NullpointerException.
package com;
public class ThrowDemo {
public static void main(String[] args) {
Sample.demo();
}
}
class Sample {
static void demo() {
try {
System.out.println("Inside demo()");
throw new NullPointerException("Exception data");
} catch(NullPointerException ne) {
System.out.println(ne);
}
}
}
Output
Inside demo()
Java.lang.NullPointerException : Exception data
In this program, we are using throw clause to throw NullPointerException class object. Then it is caught and its details are displayed in catch block.
Throws Example
Example to explain the use of throws clause.
package com;
import java.io.*;
public class Ex1 {
public static void main(String args[]) throws IOException {
Sample s = new Sample();
s.accept();
s.display();
}
}
class Sample {
private String name;
void accept() throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
name = br.readLine();
}
void display() {
System.out.println("Name: " + name);
}
}
Output
Programmer
Name : Programmer
In this program we are using throws clause to throw out an exception without handling it from a method.
Comment below if you found any mistake or have queries regarding above tutorial for difference between throw and throws in Java.
Throw and throws are keywords are used to deal with exception handling in java program. Throw keyword is used to throw exception to the runtime to handle it. Throws keyword in method signature to let caller program know the exceptions that might be thrown by the method.