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Exception Handling
Why We need Exception Handling ?
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Exception01.java
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public class Exception01 {
public static void main(String[] args) {
double a = 5/0;
System.out.println(a);
System.out.println("Reached the end of the program");
}
}
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C:\temp> java Exception01
Exception in thread "main" java.lang.ArithmeticException: / by zero
at Exception01.main(Exception01.java:5)
NOTE : Program crashed and 'System.out.println("Reached the end of the program");' is not executed.
How to Capture the Exceptions ?
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Exception02.java
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public class Exception02 {
public static void main(String[] args) {
try {
double a = 5/0;
System.out.println(a);
} catch (Exception e) {
System.out.println("An Exception occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
};
System.out.println("Reached the end of the program");
}
}
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C:\temp> java Exception02
An Exception occurred with following details :
java.lang.ArithmeticException: / by zero <-- System.out.println(" " + e);
java.lang.ArithmeticException: / by zero <-- System.out.println(" " + e.toString());
java.lang.ArithmeticException: / by zero <-- e.printStackTrace();
at Exception02.main(Exception02.java:8)
class java.lang.ArithmeticException <-- System.out.println(" " + e.getClass());
/ by zero <--
Reached the end of the program <-- System.out.println("Reached the end of the program");
NOTE : Exception occurred but program move forward
How to Capture a Specific Exception ?
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Exception03.java
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public class Exception03 {
public static void main(String[] args) {
try {
double a = 5/0;
System.out.println(a);
} catch (ArithmeticException e) {
System.out.println("An ArithmeticException occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
};
System.out.println("Reached the end of the program");
}
}
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C:\temp> java Exception03
An ArithmeticException occurred with following details :
java.lang.ArithmeticException: / by zero <-- System.out.println(" " + e);
java.lang.ArithmeticException: / by zero <-- System.out.println(" " + e.toString());
java.lang.ArithmeticException: / by zero <-- e.printStackTrace();
at Exception03.main(Exception03.java:8)
class java.lang.ArithmeticException <-- System.out.println(" " + e.getClass());
/ by zero <-- System.out.println(" " + e.getMessage));
Reached the end of the program <-- System.out.println("Reached the end of the program");
NOTE : Exception occurred but program move forward
How to Capture a Multiple Exceptions ?
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Exception04.java
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public class Exception04 {
public static void main(String[] args) {
try {
int ary[]= {0,1,2,3,4};
ary[5]=30;
} catch (ArithmeticException e) {
System.out.println("An ArithmeticException occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("An ArrayIndexOutOfBoundsException occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} catch (Exception e) { // This part is executed if the exception is not trapped above
System.out.println("An Exception occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} ;
System.out.println("Reached the end of the program");
}
}
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C:\temp> java Exception04
An ArrayIndexOutOfBoundsException occurred with following details :
java.lang.ArrayIndexOutOfBoundsException: 5 <-- System.out.println(" " + e);
java.lang.ArrayIndexOutOfBoundsException: 5 <-- System.out.println(" " + e.toString());
java.lang.ArrayIndexOutOfBoundsException: 5 <-- e.printStackTrace();
at Exception04.main(Exception04.java:12)
class java.lang.ArrayIndexOutOfBoundsException <-- System.out.println(" " + e.getClass());
5 <-- System.out.println(" " + e.getMessage());
Reached the end of the program <-- System.out.println("Reached the end of the program");
NOTE : Exception occurred but program move forward
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Exception05.java
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import java.io.*;
public class Exception05 {
public static void main(String[] args) {
try {
int ary[]= {0,1,2,3,4};
ary[5]=30;
} catch (ArithmeticException e) {
System.out.println("An ArithmeticException occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("An ArrayIndexOutOfBoundsException occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} catch (Exception e) { // This part is executed if the exception is not trapped above
System.out.println("An Exception occurred with following details :");
System.out.println(" " + e);
System.out.println(" " + e.toString());
System.out.print(" ");
e.printStackTrace();
System.out.println(" " + e.getClass());
System.out.println(" " + e.getMessage());
} ;
System.out.println("Reached the end of the program");
}
}
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C:\temp> java Exception05
An Exception occurred with following details :
java.io.FileNotFoundException: input.txt (The system cannot find the file specified)
<-- System.out.println(" " + e);
java.io.FileNotFoundException: input.txt (The system cannot find the file specified)
<-- System.out.println(" " + e.toString());
java.io.FileNotFoundException: input.txt (The system cannot find the file specified)
<-- e.printStackTrace();
at java.io.FileInputStream.open0(Native Method)
at java.io.FileInputStream.open(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
at Exception05.main(Exception05.java:11)
java.io.FileNotFoundException <-- System.out.println(" " + e.getClass());
input.txt (The system cannot find the file specified)
<-- System.out.println(" " + e.getMessage());
Reached the end of the program <-- System.out.println("Reached the end of the program");
NOTE : Exception occurred but program move forward
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