Built-in Exceptions in Java with examples

Difficulty Level : Easy
Last Updated : 04 Jul, 2020

Built-in exceptions are the exceptions which are available in Java libraries. These exceptions are suitable to explain certain error situations. Below is the list of important built-in exceptions in Java.
Examples of Built-in Exception:

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Arithmetic exception : It is thrown when an exceptional condition has occurred in an arithmetic operation.

// Java program to demonstrate 
// ArithmeticException
class ArithmeticException_Demo {
public static void main(String args[])
    {
        try {
            int a = 30, b = 0;
            int c = a / b; // cannot divide by zero
            System.out.println("Result = " + c);
        }
        catch (ArithmeticException e) {
            System.out.println("Can't divide a number by 0");
        }
    }
}

Output:

Can't divide a number by 0

ArrayIndexOutOfBounds Exception : It is thrown to indicate that an array has been accessed with an illegal index. The index is either negative or greater than or equal to the size of the array.

// Java program to demonstrate 
// ArrayIndexOutOfBoundException
class ArrayIndexOutOfBound_Demo {
public static void main(String args[])
    {
        try {
            int a[] = new int[5];
            a[6] = 9; // accessing 7th element in an array of
            // size 5
        }
        catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Array Index is Out Of Bounds");
        }
    }
}

Output:

Array Index is Out Of Bounds

ClassNotFoundException : This Exception is raised when we try to access a class whose definition is not found.

// Java program to illustrate the 
// concept of ClassNotFoundException
class Bishal {
  
} class Geeks {
  
} class MyClass {
public static void main(String[] args)
    {
        Object o = class.forName(args[0]).newInstance();
        System.out.println("Class created for" + o.getClass().getName());
    }
}

Output:

ClassNotFoundException

FileNotFoundException : This Exception is raised when a file is not accessible or does not open.

// Java program to demonstrate 
// FileNotFoundException
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
class File_notFound_Demo {
  
public static void main(String args[])
    {
        try {
  
            // Following file does not exist
            File file = new File("E:// file.txt");
  
            FileReader fr = new FileReader(file);
        }
        catch (FileNotFoundException e) {
            System.out.println("File does not exist");
        }
    }
}

Output:

File does not exist

IOException : It is thrown when an input-output operation failed or interrupted

// Java program to illustrate IOException
import java.io.*;
class Geeks {
public static void main(String args[])
    {
        FileInputStream f = null;
        f = new FileInputStream("abc.txt");
        int i;
        while ((i = f.read()) != -1) {
            System.out.print((char)i);
        }
        f.close();
    }
}

Output:

error: unreported exception IOException; must be caught or declared to be thrown

InterruptedException : It is thrown when a thread is waiting, sleeping, or doing some processing, and it is interrupted.

// Java Program to illustrate
// InterruptedException
class Geeks {
public static void main(String args[])
    {
        Thread t = new Thread();
        t.sleep(10000);
    }
}
Output:
```
error: unreported exception InterruptedException; must be caught or declared to be thrown
```

NoSuchMethodException : t is thrown when accessing a method which is not found.

// Java Program to illustrate 
// NoSuchMethodException
class Geeks {
public Geeks()
    {
        Class i;
        try {
            i = Class.forName("java.lang.String");
            try {
                Class[] p = new Class[5];
            }
            catch (SecurityException e) {
                e.printStackTrace();
            }
            catch (NoSuchMethodException e) {
                e.printStackTrace();
            }
        }
        catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
  
public static void main(String[] args)
    {
        new Geeks();
    }
}

Output:

error: exception NoSuchMethodException is never thrown 
in body of corresponding try statement

NullPointerException : This exception is raised when referring to the members of a null object. Null represents nothing

// Java program to demonstrate NullPointerException
class NullPointer_Demo {
public static void main(String args[])
    {
        try {
            String a = null; // null value
            System.out.println(a.charAt(0));
        }
        catch (NullPointerException e) {
            System.out.println("NullPointerException..");
        }
    }
}

Output:

NullPointerException..

NumberFormatException : This exception is raised when a method could not convert a string into a numeric format.

// Java program to demonstrate 
// NumberFormatException
class NumberFormat_Demo {
public static void main(String args[])
    {
        try {
            // "akki" is not a number
            int num = Integer.parseInt("akki");
  
            System.out.println(num);
        }
        catch (NumberFormatException e) {
            System.out.println("Number format exception");
        }
    }
}

Output:

Number format exception

StringIndexOutOfBoundsException : It is thrown by String class methods to indicate that an index is either negative than the size of the string.

// Java program to demonstrate 
// StringIndexOutOfBoundsException
class StringIndexOutOfBound_Demo {
public static void main(String args[])
    {
        try {
            String a = "This is like chipping "; // length is 22
            char c = a.charAt(24); // accessing 25th element
            System.out.println(c);
        }
        catch (StringIndexOutOfBoundsException e) {
            System.out.println("StringIndexOutOfBoundsException");
        }
    }
}

Output:

StringIndexOutOfBoundsException

Some other important Exceptions

ClassCastException

// Java Program to illustrate
// ClassCastException
class Test {
public static void main(String[] args)
    {
        String s = new String("Geeks");
        Object o = (Object)s;
        Object o1 = new Object();
        String s1 = (String)o1;
    }
}

Output:

Exception in thread "main" java.lang.ClassCastException: 
java.lang.Object cannot be cast to java.lang.String

StackOverflowError

// Java Program to illustrate 
// StackOverflowError
class Test {
public static void main(String[] args)
    {
        m1();
    }
public static void m1()
    {
        m2();
    }
public static void m2()
    {
        m1();
    }
}

Output:

Exception in thread "main" java.lang.StackOverflowError

NoClassDefFoundError

// Java Program to illustrate
// NoClassDefFoundError
class Test //
    {
public static void main(String[] args)
    {
        System.out.println("HELLO GEEKS");
    }
}

Output:

Note: If the corresponding Test.class file is not found 
during compilation then we will get Run-time Exception
saying Exception in thread "main" java.lang.NoClassDefFoundError

ExceptionInInitializerError
Code 1:

// Java Program to illustrate 
// ExceptionInInitializerError
class Test {
    static int x = 10 / 0;
public static void main(String[] args)
    {
    }
}

Output:

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.ArithmeticException: / by zero

Code 2 :

// Java Program to illustrate 
// ExceptionInInitializerError
class Test {
    static
    {
        String s = null;
        System.out.println(s.length());
    }
public static void main(String[] args)
    {
    }
}

Output:

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException

Explanation : The above exception occurs whenever while executing static variable assignment and static block if any Exception occurs.

IllegalArgumentException

// Java Program to illustrate 
// IllegalArgumentException
class Test {
public static void main(String[] args)
    {
        Thread t = new Thread();
        Thread t1 = new Thread();
        t.setPriority(7); // Correct
        t1.setPriority(17); // Exception
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException

Explanation:The Exception occurs explicitly either by the programmer or by API developer to indicate that a method has been invoked with Illegal Argument.

IllegalThreadStateException

// Java Program to illustrate 
// IllegalStateException
class Test {
public static void main(String[] args)
    {
        Thread t = new Thread();
        t.start();
        t.start();
    }
}

Output:

Exception in thread "main" java.lang.IllegalThreadStateException

Explanation : The above exception rises explicitly either by programmer or by API developer to indicate that a method has been invoked at wrong time.

AssertionError

// Java Program to illustrate 
// AssertionError
class Test {
public static void main(String[] args)
    {
        // If x is not greater than or equal to 10
        // then we will get the run-time exception
        assert(x >= 10);
    }
}

Output:

Exception in thread "main" java.lang.AssertionError

Explanation : The above exception rises explicitly by the programmer or by API developer to indicate that assert statement fails.

This article is contributed by Bishal Kumar Dubey. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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