StringTokenizer in JAVA

The StringTokenizer class allows an application to break a string into tokens. The tokenization method is much simpler than the one used by the StreamTokenizer class. The StringTokenizer do not distinguish among identifiers, numbers, and quoted strings, nor do they recognize and skip comments.

The set of delimiters (the characters that separate tokens) may be specified either at creation time or on a per-token basis.

An instance of StringTokenizer behaves in one of two ways, depending on whether it was created with the returnDelims having the value True or False :

• If the flag is Flase , delimiter characters serve to separate tokens. A token is a maximal sequence of consecutive characters that are not delimiters.
• If the flag is True , delimiter characters are themselves considered to be tokens. A token is thus either one delimiter character, or a maximal sequence of consecutive characters that are not delimiters.

A StringTokenizer object internally maintains a current position within the string to be tokenized. Some operations advance this current position past the characters processed.

A token is returned by taking a substring of the string that was used to create the StringTokenizer object.

Example without Delimiter:-

StringTokenizer st = new StringTokenizer("Example Of String Tokenizer");
while (st.hasMoreTokens()) {
System.out.println(st.nextToken());
}

Output
=====
Example
of
String
Tokenizer

Example with Delimiter:-

StringTokenizer st = new StringTokenizer("1$2$3$4","$");
while (st.hasMoreTokens()) {
System.out.println(st.nextToken());
}

Output
=====
1
2
3
4

Open a File in Runtime in Java

Open a File in Runtime in Java:

1.Create a Object For Process

2.exec is a method to open a File in Runtime

3.In the exec Method, we can give all the command which can be give in the Run Window

Process process=Runtime.getRuntime().exec("notepad d:\demo.txt");

4.If it cannot Work,Copy Exe File and Paste it in C:\Windows\System32

Java with Sql Server

How to Connect Java with Sql Server :

1.import sql package

2.Give all the Supporting class in class.forName

3.Give Ipaddress or Computer Name in dburl or in getConnection

4.Use 1433 port Number as Default Port.

5.Give Username and Password in getConnection

6.Open the Connection using createStatement

7.Execute the query String using executeQuery Statement

8.Fetch the Record one by one Using ResultSet

9.Close the Connection

import java.io.*;
import java.sql.*;
public class sqlserverConnection
{
public static String dburl=”jdbc:mysql://localhost:1433”;
public static String username=”admin”;
public static String pwd=”pass”;
public static Connection con=null;
public static Statement stmt=null;
public static ResultSet rs=null;

public static void main(String[] args)
{
try {

Class.forName( "com.microsoft.jdbc.sqlserver.SQLServerDriver" );
con=DriverManager.getConnection(dburl,username,pwd);
stmt=con.createStatement();
rs=stmt.executeQuery(”SELECT * FROM demo”);
while(rs.next())
{
String name=rs.getString(1);
}
}
catch(SQLException sqlExcp)
{
sqlExcp.printStackTrace();
}
}
}

Java with Mysql

How to Connect Java with Mysql:

1.import sql package

2.Give all the Supporting class in class.forName

3.Give Ipaddress or Computer Name in dburl or in getConnection

4.Give Username and Password in getConnection

5.Open the Connection using createStatement

6.Execute the query String using executeQuery Statement

7.Fetch the Record one by one Using ResultSet

8..mysqldemo is a schema name

9.Close the Connection

import java.io.*;
import java.sql.*;
public class MysqlConnection
{
public static String dburl=”jdbc:mysql://localhost/mysqldemo”;
public static String username=”root”;
public static String pwd=”root”;
public static Connection con=null;
public static Statement stmt=null;
public static ResultSet rs=null;

public static void main(String[] args)
{
try {

Class.forName(”org.gjt.mm.mysql.Driver”);
(or)
Class.forName(”com.mysql.jdbc.Driver”);//use this

con=DriverManager.getConnection(dburl,username,pwd);
stmt=con.createStatement();
rs=stmt.executeQuery(”SELECT * FROM demo”);
while(rs.next())
{
String name=rs.getString(1);
}
}
catch(SQLException sqlExcp)
{
sqlExcp.printStackTrace();
}
}
}

Accessing Private Variable

Reflection in java:
Reflection is the mechanism by which Java exposes the features of a class during runtime, allowing Java programs to enumerate and access a class’ methods, fields, and constructors as objects. In other words, there are object based mirrors which reflect the Java object model, and you can use these objects to access an object’s features using runtime API constructs instead of compile time language constructs.

Each object instance has a getClass() method, inherited from java.lang.Object, which returns an object with the runtime representation of that object’s class; this object is an instance of the java.lang.Class.This object in turn has methods which return the fields, methods, constructors, superclass, and other properties of that class.

You can use these reflection objects to access fields, invoke methods, or instantiate instances, all without having compile time dependencies on those features. The Java runtime provides the corresponding classes for reflection. Most of the Java classes which support reflection are in the java.lang.reflect package.

Accessing Private Features with Reflection:
All features of a class can be obtained via Reflection, including Access to private methods & variables.Setting the Accessible flag in a reflected object of java.lang.reflect.AccessibleObject class allows us to read/modify a private variable that we normally wouldn’t have permission to. However, the access check can only be supressed if approved by installed SecurityManager.
The Classes java.lang.reflect.Field, java.lang.reflect.Method and java.lang.reflect.Constructor can inherit this behavior from java.lang.reflect.AccessibleObject class. The following example demonstrates read/modify access to a private variable which is normally inaccessible.

SimpleKeyPair.java

package com;

public class SimpleKeyPair {

private String privateKey = “Welcome SimpleKeyPair “; // private field

}

PrivateMemberAccessTest.java

package com;

import java.lang.reflect.Field;

public class PrivateMemberAccessTest {

public static void main(String[] args) throws Exception {

SimpleKeyPair keyPair = new SimpleKeyPair();

Class c = keyPair.getClass();

// get the reflected object

Field field = c.getDeclaredField(”privateKey”);

// set accessible true

field.setAccessible(true);

System.out.println(”Value of privateKey: ” + field.get(keyPair));

/* prints “Welcome SimpleKeyPair */

// modify the member varaible

field.set(keyPair, “Welcome PrivateMemberAccessTest”);

System.out.println(”Value of privateKey: ” + field.get(keyPair));

/* prints “PrivateMemberAccessTest” */

}

}

Output

=====

Value of privateKey: Welcome SimpleKeyPair

Value of privateKey: PrivateMemberAccessTest

how to find a string within a string

Find a String within a String:
Search a String "a Nice" is Exist or Not within a String "Have a Nice Day" in JAVA

Coding:

String s = "Have a Nice Day";
if(s.indexOf("a Nice")!=-1)
System.out.println("string exist==>");
else
System.out.println("string Not exist==>");