Nested Try-Catch Blocks
In Java we can have nested try
and catch blocks. It means that, a try statement can be inside the
block of another try. If an inner try statement does not have a matching catch
statement for a particular exception, the control is transferred to
the next try statement’s catch handlers that are expected for a matching catch
statement. This continues until one of the catch statements succeeds, or until
all of the nested try statements are done in.
If no one catch statements match, then the Java run-time system will
handle the exception.
The syntax of nested try-catch blocks is
given below:
|
try {
try {
// ...
}
catch (Exception1 e)
{
//statements to handle the exception
}
}
catch (Exception 2 e2)
{
//statements to handle the exception
}
|
Lets have an example that uses the nested try-catch
blocks
import java.io.*;
public class NestedTry{
public static void main (String args[])throws IOException {
int num=2,res=0;
try{
FileInputStream fis=null;
fis = new FileInputStream (new File (args[0]));
try{
res=num/0;
System.out.println("The result is"+res);
}
catch(ArithmeticException e){
System.out.println("divided by Zero");
}
}
catch (FileNotFoundException e){
System.out.println("File not found!");
}
catch(ArrayIndexOutOfBoundsException e){
System.out.println("Array index is Out of bound! Argument required");
}
catch(Exception e){
System.out.println("Error.."+e);
}
}
}
|
Output of the program:
| C:\Roseindia\>javac
NestedTry.java
C:\Roseindia\>java NestedTry
Array index is Out of bound!
Argument required
|
In this given example we have implemented nested try-catch blocks concept
where an inner try block is kept with in an outer try block, that's catch
handler will handle the arithmetic exception. But before that an ArrayIndexOutOfBoundsException
will be raised, if a file name is not passed as an argument while running the
program. Now lets see, what will be
the output if we pass the file name student as an argument.
| C:\Roseindia\>javac
NestedTry.java
C:\Roseindia\>java NestedTry student.txt
File not found!
|
If the outer try block's statements run
successfully then the inner try will raise an ArithmeticException as:
| C:\Roseindia\>javac
NestedTry.java
C:\Roseindia\>java NestedTry student.txt
divided by Zero
|
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