Errors V/s Exceptions In Java

Difficulty Level : Easy
Last Updated : 24 Jul, 2018

Errors V/s Exceptions In Java

Error : An Error “indicates serious problems that a reasonable application should not try to catch.”
Both Errors and Exceptions are the subclasses of java.lang.Throwable class. Errors are the conditions which cannot get recovered by any handling techniques. It surely cause termination of the program abnormally. Errors belong to unchecked type and mostly occur at runtime. Some of the examples of errors are Out of memory error or a System crash error.

// Java program illustrating stack overflow error 
// by doing infinite recursion 
  
class StackOverflow { 
    public static void test(int i) 
    { 
        // No correct as base condition leads to 
        // non-stop recursion. 
        if (i == 0) 
            return; 
        else { 
            test(i++); 
        } 
    } 
} 
public class ErrorEg { 
  
    public static void main(String[] args) 
    { 
  
        // eg of StackOverflowError 
        StackOverflow.test(5); 
    } 
} 

Output:

Exception in thread "main" java.lang.StackOverflowError
    at StackOverflow.test(ErrorEg.java:7)
    at StackOverflow.test(ErrorEg.java:7)
    at StackOverflow.test(ErrorEg.java:7)
    at StackOverflow.test(ErrorEg.java:7)
    at StackOverflow.test(ErrorEg.java:7)
...

Exceptions : An Exception “indicates conditions that a reasonable application might want to catch.”
Exceptions are the conditions that occur at runtime and may cause the termination of program. But they are recoverable using try, catch and throw keywords. Exceptions are divided into two catagories : checked and unchecked exceptions. Checked exceptions like IOException known to the compiler at compile time while unchecked exceptions like ArrayIndexOutOfBoundException known to the compiler at runtime. It is mostly caused by the program written by the programmer.

// Java program illustrating exception thrown 
// by AritmeticExcpetion class 
  
public class ExceptionEg { 
  
    public static void main(String[] args) 
    { 
        int a = 5, b = 0; 
  
        // Attempting to divide by zero 
        try { 
            int c = a / b; 
        } 
        catch (ArithmeticException e) { 
            e.printStackTrace(); 
        } 
    } 
} 

Output:

java.lang.ArithmeticException: / by zero
    at ExceptionEg.main(ExceptionEg.java:8)

Summary of Differences

Errors	Exceptions
Recovering from Error is not possible.	We can recover from exceptions by either using try-catch block or throwing exceptions back to caller.
All errors in java are unchecked type.	Exceptions include both checked as well as unchecked type.
Errors are mostly caused by the environment in which program is running.	Program itself is responsible for causing exceptions.
Errors occur at runtime and not known to the compiler.	All exceptions occurs at runtime but checked exceptions are known to compiler while unchecked are not.
They are defined in java.lang.Error package.	They are defined in java.lang.Exception package
Examples : java.lang.StackOverflowError, java.lang.OutOfMemoryError	Examples : Checked Exceptions : SQLException, IOException Unchecked Exceptions : ArrayIndexOutOfBoundException, NullPointerException, ArithmeticException.

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