Difference between throw and throws in java

by Online Tutorials Library July 22, 2022

Difference between throw and throws in Java

The throw and throws is the concept of exception handling where the throw keyword throw the exception explicitly from a method or a block of code whereas the throws keyword is used in signature of the method.

There are many differences between throw and throws keywords. A list of differences between throw and throws are given below:

Sr. no.	Basis of Differences	throw	throws
1.	Definition	Java throw keyword is used throw an exception explicitly in the code, inside the function or the block of code.	Java throws keyword is used in the method signature to declare an exception which might be thrown by the function while the execution of the code.
2.	Type of exceptionUsing throw keyword, we can only propagate unchecked exception i.e., the checked exception cannot be propagated using throw only.	Using throws keyword, we can declare both checked and unchecked exceptions. However, the throws keyword can be used to propagate checked exceptions only.
3.	Syntax	The throw keyword is followed by an instance of Exception to be thrown.	The throws keyword is followed by class names of Exceptions to be thrown.
4.	Declaration	throw is used within the method.	throws is used with the method signature.
5.	Internal implementation	We are allowed to throw only one exception at a time i.e. we cannot throw multiple exceptions.	We can declare multiple exceptions using throws keyword that can be thrown by the method. For example, main() throws IOException, SQLException.

Java throw Example

TestThrow.java

  public class TestThrow {  //defining a method  public static void checkNum(int num) {  if (num < 1) {  throw new ArithmeticException(“nNumber is negative, cannot calculate square”);  }  else {  System.out.println(“Square of ” + num + ” is ” + (num*num));  }  }  //main method  public static void main(String[] args) {  TestThrow obj = new TestThrow();  obj.checkNum(-3);  System.out.println(“Rest of the code..”);  }  }  

Output:

Difference between throw and throws in Java

Java throws Example

TestThrows.java

  public class TestThrows {  //defining a method  public static int divideNum(int m, int n) throws ArithmeticException {  int div = m / n;  return div;  }  //main method  public static void main(String[] args) {  TestThrows obj = new TestThrows();  try {  System.out.println(obj.divideNum(45, 0));  }  catch (ArithmeticException e){  System.out.println(“nNumber cannot be divided by 0”);  }    System.out.println(“Rest of the code..”);  }  }  

Output:

Difference between throw and throws in Java

Java throw and throws Example

TestThrowAndThrows.java

  public class TestThrowAndThrows  {      // defining a user-defined method      // which throws ArithmeticException      static void method() throws ArithmeticException      {          System.out.println(“Inside the method()”);          throw new ArithmeticException(“throwing ArithmeticException”);      }      //main method      public static void main(String args[])      {          try          {              method();          }          catch(ArithmeticException e)          {              System.out.println(“caught in main() method”);          }      }  }  

Output:

Difference between throw and throws in Java

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