Joshi: Presentation By

Presentation by:

JOSHI

String

String It is an Object of constant with group of characters. It will not allow to modify as it is immutable. Every modification creates a new String Object. Creating string:

String s=null; String s1=“Idea Labs”; String s2=new String(“Idea Labs”); String s3=s2; String s4=new String(s2); String s5=new String(char[ ], int, int); String s6=new String(byte[ ], int, int);

String • String1==String2 – compares references of two variables

• String1.equals(String2); • String1.equalsIgnoreCase(String2); – compares the values of two strings if equal returns true else returns false

StringTokenizer • An Object created on String to break a String into tokens. Constructors

StringTokenizer(String str) StringTokenizer(String str, String delim) StringTokenizer(String str, String delim, boolean returnDelims) while (st.hasMoreTokens()) { println(st.nextToken()); }

Exception Handling

PROGRAMMING ERRORS

Syntax Errors /

Logical Errors /

Compilation Errors

Runtime Errors

Exception

Exception Handling • Exception is Logical Error/ Runtime Error which abrupt the execution of application. • Depending on provided values in the statement, an exception may or may not occur. Ex: c = a / b ; • If any statement is going throw an Exception, it should be properly handled to overcome the abruption of the application.

try • Try is block of statements which may throw exceptions. • The statements throws an exception or exceptions raising must be there in try block to handle it. • One try block can have any number of handlers.

catch • Catch is an handler of exception thrown from the try block. • Catch should immediately follow the try block. • One try can have one catch or any number of catches but they should be continues.

try { statements; } catch(XXXException e) { handling statements; } catch(YYYException e) { handling statements; }

throw • It is used to throw an Object of Exception type or any User Defined Exceptions. • ‘throw’ must be used from try block only to handle it properly. Exception e=new Exception(); Throw e; or throw new Exception();

Exception Checked Exception

Unchecked Exception

Examples:

Examples:

IOException

ArithmeticException

RemoteException

FileNotFoundException

SocketException

NumberFormatException

AllUserDefined

ArrayIndexOutOfBounds

Exceptions

Exception

throws • ‘throws’ is used to specify Exception in method declaration from where the checked exceptions are thrown. syntax: returntype method(Args) throws CheckedException { statements; }

User Defined Exceptions • A class extended from Exception by overriding the toString() method. • These are used to raise an exception on some conditions, restrictions, validations etc. • All the user defined exceptions are Checked Exceptions which must be specified with a ‘throws’ keyword.

class MyException extends Exception { properties; constructor();

public String toString() { return Statement; } }