JAVA EXCEPTION HANDLING, Exams of Java Programming

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ExceptionException

HandlingHandling

G.MANIKANDANG.MANIKANDAN

SAP / ICT / SOCSAP / ICT / SOC

Acknowledgement

• Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0- 13 - 222158 - 6
• Program images from - Schildt

Checked ExceptionChecked Exception - - ExampleExample

Checked Exception - Example import java.io.*; class filedemo { public static void main(String args[]) { FileInputStream f=new FileInputStream("filedemo.java"); int size=f.available(); System.out.print(size); } } filedemo.java

Checked Exception - Example import java.io.*; class filedemo { public static void main(String args[]) throws Exception { FileInputStream f=new FileInputStream("filedemo.java"); int size=f.available(); System.out.print(size); } } E:\slides\Java - 2020 \Unit - I>javac filedemo.java E:\slides\Java - 2020 \Unit - I>java filedemo 211 filedemo.java

Using try and catchUsing try and catch

Multiple catch ClausesMultiple catch Clauses

Multiple catch Clauses

Limitation

Error

throws

Catch or Declare Checked Exceptions Java forces you to deal with checked exceptions. If a method declares a checked exception (i.e., an exception other than Error or RuntimeException), you must invoke it in a try-catch block or declare to throw the exception in the calling method. For example, suppose that method p1 invokes method p2 and p2 may throw a checked exception (e.g., IOException), you have to write the code as shown in (a) or (b). void p1() { try { p2(); } catch (IOException ex) { ... } } (a) (b) void p1() throws IOException { p2(); }

Declaring Exceptions Every method must state the types of checked exceptions it might throw. This is known as declaring exceptions. public void myMethod() throws IOException public void myMethod() throws IOException, OtherException

Throwing Exceptions When the program detects an error, the program can create an instance of an appropriate exception type and throw it. This is known as throwing an exception. Here is an example, throw new TheException(); TheException ex = new TheException(); throw ex;