Hi friend,

import java.io.*;
import java.io.IOException;

public class StringReverseExam{
public static void main(String[] args) throws IOException{
BufferedReader buff = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter something string!");
String sre = buff.readLine();
System.out.println(ReverseString.reverseIt(sre));
}
}
class ReverseString{
public static String reverseIt(String source) {
int i, len = source.length();
StringBuffer dest = new StringBuffer(len);
for (i = (len - 1); i >= 0; i--)
dest.append(source.charAt(i));
return dest.toString();
}
}

---------------------------------

import java.io.*;
import java.util.*;

public class Concatenation {
private final long start;

public Concatenation(){
start = System.currentTimeMillis();
}
public long getElapsed(){
return System.currentTimeMillis() - start;
}
}

public class StringConcatention{
static final int n = 47500;

public static void main(String args[]){
// build up string using +
Concatenation con = new Concatenation();
String str1 = "";
for (int i = 1; i <= n; i++) {
str1 = str1 + "*";
}
System.out.println("elapsed time #1 = " + con.getelapsed());
// build up string using stringbuffer
con = new Concatenation();
stringbuffer sb = new stringbuffer();
for(int i = 1; i <= n; i++){
sb.append("*");
}
String str2 = sb.tostring();
System.out.println("elapsed time #2 = " + con.getelapsed());
// sanity check
if (!str1.equals(str2)){
System.out.println("str1/str2 mismatch");
}
}
}

------------------------------

read for more information,

http://www.roseindia.net/java/example/java/util/CapturedText.shtml