Course:
Learn Java Programming
[post-views]
In this lesson, you will learn
try {
// Code that might throw multiple types of exceptions
}
catch (ExceptionType1 e1) {
// Handling code for ExceptionType1
}
catch (ExceptionType2 e2) {
// Handling code for ExceptionType2
}
/* You can have more catch blocks
for additional exception types */
public class MultipleCatchExample1 {
public static void main(String[] args) {
int[] numbers = {5, 10, 15, 20, 25};
int num=5;
try {
int x=numbers[5] / num-numbers[1];
/* This line can throw both ArrayIndexOutOfBoundsException
* and ArithmeticException
*/
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Array index is out of bounds!");
} catch (ArithmeticException e) {
System.out.println("Cannot divide by zero!");
}
int y=numbers[1] / numbers[0];
System.out.println("Y="+y);
}
}
Output
Array index is out of bounds!
Y=2
public class MulipleCatchExample2 {
public static void main(String[] args) {
try {
int a = args.length;
System.out.println("a = " + a);
int b = 12 / a;
int c[] = { 1 };
c[12] = 99;
}
catch(ArithmeticException e) {
System.out.println("Divide by 0: " + e);
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println("Array index oob: " + e);
}
System.out.println("After try/catch blocks.");
}
}
Test Case-1: Without passing command line arguments
Run: java MulipleCatchExample2
a = 0
Divide by 0: java.lang.ArithmeticException: / by zero
After try/catch blocks.
Test Case-2: Passing command line arguments
Run: java MulipleCatchExample2 5
a = 1
Array index oob: java.lang.ArrayIndexOutOfBoundsException:
Index 42 out of bounds for length 1
After try/catch blocks.
When you use multiple catch statements, it is important to remember that exception subclasses must come before any of their superclasses.
This is because a catch statement that uses a superclass will catch exceptions of that type plus any of its subclasses. Thus, a subclass would never be reached if it came after its superclass. Further, in Java, unreachable code is an error.
Let us understand this using an example.
/*
* A subclass must come before its superclass in a series of
* catch statements. If not, unreachable code will be
* created and a compile-time error will result.
*/
public class MulipleCatchExample3 {
public static void main(String[] args) {
try {
int x = 0;
System.out.println("a = " + a);
int b = 12 / a;
int c[] = { 1 };
c[12] = 99;
}
catch (Exception e) {
System.out.println("Generic Exception catch.");
}
//ERROR – the following exceptions are unreachable
catch(ArithmeticException e) {
System.out.println("Divide by 0: " + e);
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println("Array index oob: " + e);
}
}
}
The try statement can be inside another try.
try {
// Outer try block
try {
// Inner try block
} catch (ExceptionType1 e1) {
// Handling code for ExceptionType1
}
} catch (ExceptionType2 e2) {
// Handling code for ExceptionType2
}
<pre class="wp-block-syntaxhighlighter-code">public class NestedTryExample1 {
public static void main(String[] args) {
try {
int x = args.length;
/* If no command-line args are present,
* the following statement will generate
* a divide-by-zero exception. */
int y = 12 / x;
System.out.println("x = " + x);
try { // nested try block
/* If one command-line arg is used,
* then a divide-by-zero exception
* will be generated by the following code. */
if(x==1) x = x/(x-x); // division by zero
/* If two command-line args are used,
* then generate an out-of-bounds exception. */
if(x==2) {
int numbers[] = {1,2,3,4,5};
numbers[12] = 20; // generate an out-of-bounds exception
}
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println("Array index out-of-bounds: " + e);
}
} //outer try close
catch(ArithmeticException e) {
System.out.println("Divide by 0: " + e);
}
}
}<br /><br /></pre>
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