throws Keyword in Java

Last Updated: 06 March, 2023

In Java, the throws keyword is used in a method signature and declares which exceptions can be thrown from a method.

Exceptions can be propagated in the call stack using the throws keyword. When a method declares that it throws an exception, it is not required to handle the exception. The caller of a method that throws exceptions is required to handle the exceptions (or throw them to its caller, and so on) so that the flow of the program can be maintained.

The throws keyword allows us to declare multiple exceptions; if we are declaring multiple exceptions, each exception should be separated by a comma in the declaration.

Throws only handles checked exceptions. Unchecked exceptions don’t need to be thrown or handled explicitly in code.

Syntax:

  return_type method_name (arguments) throws Exception1, Exception2, … {  }

Java throws example

  public class ThrowsExample1 {
    public static void calculate() throws ArithmeticException, ArrayIndexOutOfBoundsException {
      int num[] = { 10, 20 };
      System.out.println("Division Result: " + num[0] / 2);
      System.out.println("Division Result: " + num[5] / 2);
    }
  
    public static void main(String[] args) {
      try {
        calculate();
      } catch (ArithmeticException e) {
        System.out.println("Arithmetic Exception thrown" + e.getMessage());
      } catch (ArrayIndexOutOfBoundsException e) {
        System.out.println("ArrayIndexOutOfBounds Exception thrown" + e.getMessage());
      }
    }
  }

Output

Division Result: 5
ArrayIndexOutOfBounds Exception thrownIndex 5 out of bounds for length 2

Java throws example

  
  import java.io.BufferedWriter;
  import java.io.FileWriter;
  import java.io.IOException;
  public class ThrowsExample2 {
    public static void writeStudentRecord() throws IOException {
      BufferedWriter bw = new BufferedWriter(new FileWriter("studentRecord.txt"));
      bw.write("Name: Suresh, Roll: 21, Class: LKG");
      bw.close();
    }
    
    public static void main(String[] args) {
      try {
        writeStudentRecord();
        System.out.println("Student record added successfully...");
      } catch (IOException ioe) {
        ioe.printStackTrace();
      }
    }
  }

Output

Student record added successfully...

Here, the “writeStudentRecord” method throws an IOException and declares it using the throws keyword to its callers. The “main” method calls the “writeStudentRecord” method and handles the exception within a try-catch block, and prints the exception stack trace to the console.

throws Keyword in Java

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