How to write a java program to reverse a string without using string functions?
String a="Siva";
for(int i=0;i<=a.length()-1;i++)
{
System.out.print(a.charAt(i));
}
System.out.println("");
for(int i = a.length() - 1; i >= 0; --i)
{
System.out.print(a.charAt(i));
}
here charAt() and a.length() are string functions
This will help
public class StringReverse {
public static void main(String[] args){
String str = "Reverse";
StringBuilder sb = new StringBuilder(str);
str = sb.reverse().toString();
System.out.println("ReverseString : "+str);
}
}
There is no usage of String methods
String s = "abcdef";
char c[] = s.toCharArray();
for( int i = c.length -1; i>=0; i--)
System.out.print(c[i]);
toCharArray() string functions.Use StringBuilder class or StringBuffer class they have already a method reverse() for reversing the string
StringBuilder str = new StringBuilder("india");
System.out.println("string = " + str);
// reverse characters of the StringBuilder and prints it
System.out.println("reverse = " + str.reverse());
// reverse is equivalent to the actual
str = new StringBuilder("malayalam");
System.out.println("string = " + str);
// reverse characters of the StringBuilder and prints it
System.out.println("reverse = " + str.reverse());
http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html
Below is ugly hack. It concept but it not invoke any String methods.
import java.io.*;
import java.util.*;
public class Hello {
public static String reverceWithoutStringMethods(String word){
String result = "";
//------ Write string to file -----------
BufferedWriter writer = null;
try {
writer = new BufferedWriter( new FileWriter("tempfile"));
writer.write(word);
}
catch ( IOException e) {}
finally {
try{
if ( writer != null) writer.close( );
}
catch ( IOException e){}
}
//------ read string from file -------------
RandomAccessFile f=null;
try {
f = new RandomAccessFile("tempfile", "r"); // Open file
int length = (int) f.length(); // Get length
// Read file
byte[] data = new byte[length];
f.readFully(data);
// Reverse data
for (int i=data.length; i>=0; i--){
result += (char)data[i-1];
}
} catch(Exception e){}
finally {
try{
f.close();
}
catch (Exception e){}
}
return result;
}
public static void main(String[] args) {
System.out.println(reverceWithoutStringMethods("Test"));
System.out.println(reverceWithoutStringMethods(""));
}
}
Output:
tseT