Try and Catch in Java

Exception

When your code can throw an exception (error on run time), you can wrap that code in try and catch block.

Example: ArrayIndexOutOfBoundsException

Code

public class TryAndCatch {  	  	public static void main( String[] args ){  		String str = "Hello";  		char[] charArr = str.toCharArray();    		try {  			char lastChar = charArr[charArr.length];  			System.out.println(lastChar);  		} catch(ArrayIndexOutOfBoundsException e) {  			e.printStackTrace();  			//System.out.println("Index number out of scope");  		}  	}    }

Output

java.lang.ArrayIndexOutOfBoundsException: 5

at TryAndCatch.main(TryAndCatch.java:8)

Multiple Catch Blocks

public class TryAndCatch {  	  	public static void main( String[] args ){  		String str = "Hello";  		char[] charArr = str.toCharArray();    		try {  			char lastChar = charArr[charArr.length - 1];  			System.out.println(lastChar);  			String subStr = str.substring(8);  		} catch(ArrayIndexOutOfBoundsException e) {  			e.printStackTrace();  			//System.out.println("Index number out of scope");  		} catch(StringIndexOutOfBoundsException e) {  			System.out.println("String index out of bound!");  		}  	}    }

Output

String index out of bound!

Custom Exception

public class TryAndCatch {  	  	public static void main( String[] args ){  		String str = "Hello";  		char[] charArr = str.toCharArray();    		try {    			if (charArr.length < 10) {  				throw (new Exception("My custom exception")); //this will look for catch block  			}    			char lastChar = charArr[charArr.length - 1];  			System.out.println(lastChar);  			String subStr = str.substring(8);  		} catch(ArrayIndexOutOfBoundsException e) {  			e.printStackTrace();  			//System.out.println("Index number out of scope");  		} catch(StringIndexOutOfBoundsException e) {  			System.out.println("String index out of bound!");  		} catch(Exception e) {  			System.out.println(e.getMessage());  		}  	}    }

Output

My custom exception

Notes

• A try block must be followed by at least 1 catch block.
• e is just a name given to exception and it can be reused.
• If your code generates an exception then it will stop to that point itself and not execute further. So, even if you have 2 exceptions, only first will be displayed.