Program to toggle string's letter.

import java.io.*;
class StrToggle
{
public static void main(String arg[])
{
int i;
System.out.println("Enter the String:");
DataInputStream d=new DataInputStream(System.in);
try
{
String str=d.readLine();
char a[]=str.toCharArray();
for(i=0;i<a.length;i++)
{
if((a[i]>='a')&&(a[i]<='z'))
{
a[i]=(char)((int)a[i]-32);
}
else if(((a[i]>='A')&&(a[i]<='Z')))
{
a[i]=(char)((int)a[i]+32);
}
}
System.out.println("After convert:");
for(i=0;i<a.length;i++)
{
System.out.print(a[i]);
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Output:

Program to convert first letter of each word in string to uppercase and other in lower case.

import java.io.*;
class StrTog
{
public static void main(String arg[])
{
int i;
System.out.println("Enter the String:");
DataInputStream d=new DataInputStream(System.in);
try
{
String str=d.readLine();
char a[]=str.toCharArray();
for(i=0;i<a.length;i++)
{
if((a[i]>='a')&&(a[i]<='z'))
{
a[i]=(char)((int)a[i]-32);
}
}
for(i=1;i<a.length;i++)
{
if((a[i-1]==' ')&&((a[i]>='a')&&(a[i]<='z')))
{
a[i]=(char)((int)a[i]-32);
}

if((a[i-1]!=' ')&&((a[i]>='A')&&(a[i]<='Z')))
{
a[i]=(char)((int)a[i]+32);
}
}
System.out.println("After convert:");
for(i=0;i<a.length;i++)
{
System.out.print(a[i]);
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Output:

Program to convert String from lowercase to uppercase.

import java.io.*;
class StrUpper
{
public static void main(String args[])
{
int i;
System.out.println("Enter the Sring:");
DataInputStream d=new DataInputStream(System.in);
   try
{
String str=d.readLine();
String uper=str.toUpperCase();
System.out.println(uper);
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Output:

Program to convert String from lower case to upper case without using predefined method.

import java.io.*;
class Strup
{
public static void main(String args[])
{
int i;
System.out.println("Enter the Sring:");
DataInputStream d=new DataInputStream(System.in);
   try
{
String str=d.readLine();
char a[]=str.toCharArray();
for(i=0;i<a.length;i++)
{
if((a[i]>='a')&&(a[i]<='z'))
{
a[i]=(char)((int)a[i]-32);
}
}
for(i=0;i<a.length;i++)
{
System.out.print(a[i]);
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Output:

Program to find length of string using built-in string fuctiion.

import java.io.*;
class Len
{
    public static void main(String args[])
    {
        System.out.println("Enter a string:");
        DataInputStream s=new DataInputStream(System.in);
        try
        {
            String str=s.readLine();
            int le=str.length();
            System.out.println("String length="+le);
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
}

Output:

Program to find the length of String without using buit-in function.

import java.util.*;
class SLength
{
public static void main(String args[])
{
int len=0;
String str="Welcome to Java Programing";
char a[]=str.toCharArray();
for(int i=0;i<a.length;i++)
{
len++;
}
System.out.println("String Length="+len);
}
}