Java - Built-in Exceptions | Comprehensive Guide

Explore Java's built-in exceptions, their types, and examples of checked and unchecked exceptions with code snippets and explanations.

Java - Built-in Exceptions

Java provides several built-in exceptions through the java.lang package. These exceptions are part of the standard Java libraries and help developers handle common error scenarios.

The most general exceptions in Java are subclasses of the RuntimeException class. Since java.lang is automatically imported in all Java programs, exceptions derived from RuntimeException are readily available.

Types of Java Built-in Exceptions

Java built-in exceptions are broadly categorized into two types:

1. Checked Exceptions

Checked exceptions must be handled by the programmer during code writing. These exceptions occur during compile-time and can be managed using the try-catch block.

2. Unchecked Exceptions

Unchecked exceptions occur at runtime and do not require explicit handling by the programmer. Some common unchecked exceptions include NullPointerException, ArrayIndexOutOfBoundsException, and ArithmeticException.

Common Built-in Exceptions in Java

Java defines a wide range of exceptions for handling different error scenarios. Below is a list of commonly encountered exceptions:

Exception	Description
`ArithmeticException`	Arithmetic error, such as division by zero.
`ArrayIndexOutOfBoundsException`	Array index is out of bounds.
`ArrayStoreException`	Assignment of an incompatible type to an array element.
`ClassCastException`	Invalid type casting.
`IllegalArgumentException`	Invalid argument passed to a method.
`IllegalMonitorStateException`	Illegal monitor operation, such as waiting on an unlocked thread.
`IllegalStateException`	Invalid state of the environment or application.
`IndexOutOfBoundsException`	An index is out of bounds.
`NullPointerException`	Invalid use of a null reference.
`NumberFormatException`	Invalid conversion of a string to a numeric format.
`SecurityException`	Security violation attempt.
`StringIndexOutOfBoundsException`	Attempt to access a string outside its valid range.
`UnsupportedOperationException`	Unsupported operation encountered.
`ClassNotFoundException`	Specified class not found.
`IllegalAccessException`	Access to a class is denied.

Examples of Java Built-in Exceptions

Example 1: Demonstrating `ArithmeticException` Without try-catch

In this example, dividing a value by 0 causes an ArithmeticException. Since the exception is unchecked, it occurs at runtime and terminates the program.

Syntax


package com.tutorialsarena;

public class ExcepTest {
public static void main(String args[]) {
int b = 0;
int c = 1 / b; // Division by zero
System.out.println("c :" + c);
}
}

Output


Exception in thread "main" java.lang.ArithmeticException: / by zero
at com.tutorialsarena.ExcepTest.main(ExcepTest.java:7)

Example 2: Demonstrating `ArithmeticException` With try-catch

In this example, we handle the ArithmeticException using a try-catch block, which allows the program to continue after catching the exception.

Syntax


package com.tutorialsarena;

public class ExcepTest {
public static void main(String args[]) {
try {
    int b = 0;
    int c = 1 / b; // Division by zero
    System.out.println("c :" + c);
} catch (ArithmeticException e) {
    System.out.println("Exception thrown: " + e);
}
System.out.println("Out of the block");
}
}

Output


Exception thrown: java.lang.ArithmeticException: / by zero
Out of the block

Example 3: Demonstrating `NoSuchMethodException`

This example demonstrates a checked exception, which must either be handled or declared. The NoSuchMethodException is thrown by the getName() method, which needs proper handling or declaration to avoid compilation errors.

Syntax


package com.tutorialsarena;

public class ExcepTest {
public static void main(String args[]) {
ExcepTest excepTest = new ExcepTest();
excepTest.getName(); // Throws NoSuchMethodException
}

private String getName() throws NoSuchMethodException {
throw new NoSuchMethodException(); // Manually throwing the exception
}
}

Output


Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Unhandled exception type NoSuchMethodException
at com.tutorialsarena.ExcepTest.main(ExcepTest.java:7)

Java - Built-in Exceptions | Comprehensive Guide