Multiple catch blocks in Java

Introduction

Multiple catch blocks let you handle different errors separately in your program. This helps fix problems more clearly and safely.

When your code might cause different types of errors and you want to respond to each one differently.

When reading a file that might not exist or might have wrong data format.

When working with user input that could cause different problems like wrong number or text.

When calling methods that throw different exceptions and you want to handle each case.

Syntax

Java

try {
    // code that might throw exceptions
} catch (ExceptionType1 e1) {
    // handle ExceptionType1
} catch (ExceptionType2 e2) {
    // handle ExceptionType2
} // more catch blocks as needed

Each catch block handles one specific type of exception.

Catch blocks are checked in order; the first matching one runs.

Examples

This example catches a specific array error first, then any other error.

Java

try {
    int[] numbers = {1, 2, 3};
    System.out.println(numbers[5]);
} catch (ArrayIndexOutOfBoundsException e) {
    System.out.println("Index is out of range.");
} catch (Exception e) {
    System.out.println("Some other error happened.");
}

This example handles division by zero separately from other errors.

Java

try {
    int result = 10 / 0;
} catch (ArithmeticException e) {
    System.out.println("Cannot divide by zero.");
} catch (Exception e) {
    System.out.println("General error.");
}

Sample Program

The program tries to access an invalid array index, which causes an exception. The first catch block matches and runs, so the arithmetic error is not reached.

Java

public class MultipleCatchExample {
    public static void main(String[] args) {
        try {
            int[] arr = {1, 2, 3};
            System.out.println(arr[3]); // This will cause ArrayIndexOutOfBoundsException
            int result = 10 / 0; // This will cause ArithmeticException but won't run because of previous error
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Caught an array index error.");
        } catch (ArithmeticException e) {
            System.out.println("Caught an arithmetic error.");
        } catch (Exception e) {
            System.out.println("Caught some other error.");
        }
    }
}

Important Notes

Put more specific exceptions before general ones like Exception.

Only one catch block runs per try.

Use multiple catch blocks to give clear messages or recovery steps for different errors.

Summary

Multiple catch blocks let you handle different errors separately.

They run in order, and only the first matching one runs.

Always put specific exceptions before general ones.

Practice

1.

What is the main purpose of using multiple catch blocks in Java?

easy

A. To handle different types of exceptions separately

B. To run all catch blocks regardless of exception type

C. To improve program speed by skipping exceptions

D. To avoid using try blocks

Solution

1. Step 1: Understand exception handling

   Multiple catch blocks allow handling different exceptions in different ways.

2. Step 2: Identify the purpose

   Each catch block targets a specific exception type, so only the matching one runs.

3. Final Answer:

   To handle different types of exceptions separately -> Option A

4. Quick Check:

   Multiple catch blocks = handle exceptions separately [OK]

Hint: Multiple catch blocks handle different exceptions separately [OK]

Common Mistakes:

• Thinking all catch blocks run for one exception
• Believing catch blocks improve speed
• Confusing catch blocks with try blocks

2.

Which of the following is the correct syntax for multiple catch blocks in Java?

try {
    // code
} catch (IOException e) {
    // handle IO
} catch (Exception e) {
    // handle general
}

easy

A. try { } catch (Exception e) { } catch (IOException e) { }

B. try { } catch (IOException e) { } catch (Exception e) { }

C. try { } catch IOException e { } catch Exception e { }

D. try { } catch (Exception e) catch (IOException e) { }

Solution

1. Step 1: Check catch block order

   Specific exceptions like IOException must come before general ones like Exception.

2. Step 2: Verify syntax correctness

   Each catch block must have parentheses around exception type and variable.

3. Final Answer:

   try { } catch (IOException e) { } catch (Exception e) { } -> Option B

4. Quick Check:

   Specific before general, correct syntax [OK]

Hint: Put specific exceptions before general ones in catch blocks [OK]

Common Mistakes:

• Placing general exception before specific
• Missing parentheses in catch
• Combining catch blocks without braces

3.

What will be the output of the following code?

try {
    int[] arr = new int[2];
    System.out.println(arr[5]);
} catch (ArrayIndexOutOfBoundsException e) {
    System.out.println("Index error");
} catch (Exception e) {
    System.out.println("General error");
}

medium

A. No output

B. General error

C. ArrayIndexOutOfBoundsException

D. Index error

Solution

1. Step 1: Identify exception thrown

   Accessing arr[5] causes ArrayIndexOutOfBoundsException.

2. Step 2: Match catch block

   The first catch matches ArrayIndexOutOfBoundsException and prints "Index error".

3. Final Answer:

   Index error -> Option D

4. Quick Check:

   ArrayIndexOutOfBoundsException caught by first catch [OK]

Hint: First matching catch block runs for thrown exception [OK]

Common Mistakes:

• Thinking general catch runs first
• Expecting exception message printed
• Assuming no output on exception

4.

Find the error in this code snippet:

try {
    int a = 5 / 0;
} catch (Exception e) {
    System.out.println("Error");
} catch (ArithmeticException e) {
    System.out.println("Math error");
}

medium

A. Try block missing braces

B. Exception catch block should be removed

C. ArithmeticException catch block should come before Exception catch block

D. No error, code is correct

Solution

1. Step 1: Check catch block order

   More specific exceptions must come before general ones.

2. Step 2: Identify error

   ArithmeticException is a subclass of Exception, so its catch must be first.

3. Final Answer:

   ArithmeticException catch block should come before Exception catch block -> Option C

4. Quick Check:

   Specific before general catch order [OK]

Hint: Place specific exceptions before general ones in catch blocks [OK]

Common Mistakes:

• Putting general catch before specific
• Ignoring catch block order rules
• Assuming no compile error

5.

Consider this code:

try {
    String s = null;
    System.out.println(s.length());
} catch (NullPointerException e) {
    System.out.println("Null pointer caught");
} catch (RuntimeException e) {
    System.out.println("Runtime exception caught");
} catch (Exception e) {
    System.out.println("General exception caught");
}

What will be printed and why is the catch order important here?

hard

A. "Null pointer caught" because NullPointerException is caught first

B. "Runtime exception caught" because RuntimeException is more general

C. "General exception caught" because Exception is the base class

D. Compilation error due to catch order

Solution

1. Step 1: Identify exception thrown

   Calling length() on null throws NullPointerException.

2. Step 2: Check catch order

   NullPointerException is caught by the first catch block, which is specific and placed before general exceptions.

3. Step 3: Understand importance of order

   If general exceptions came first, specific ones would be unreachable causing compile error.

4. Final Answer:

   "Null pointer caught" because NullPointerException is caught first -> Option A

5. Quick Check:

   Specific exceptions first, correct catch order [OK]

Hint: Catch specific exceptions before general ones to avoid errors [OK]

Common Mistakes:

• Assuming general catch runs first
• Ignoring NullPointerException specifics
• Not knowing catch block order matters