A String can be converted to an Array of characters and the array is inverted looping from the end to the beginning.
StringBuilder toReturn = new StringBuilder();
char[] tab = input.toCharArray();
for( int i = tab.length-1 ; i >= 0 ; i--){
toReturn.append( tab[i] );
}
return toReturn.toString();
This example creates a method called reverse that converts a String to a CharArray. It loops on all the Characters from the last one to the first one and adds it to a StringBuilder. The output is then returned.
This method is called with 2 sample Strings. The first method reverse is called twice with the output of the first call showing that the output is the same as the input.
public class StringReverse {
public static String reverse(String input){
StringBuilder sb = new StringBuilder();
char[] tab = input.toCharArray();
for( int i = tab.length-1 ; i >= 0 ; i--){
sb.append( tab[i] );
}
return sb.toString();
}
public static void main(String[] argv) {
String test = "This is a test";
// Call reverse
String output = reverse( test );
System.out.println( test + " => " + output );
// Same test calling reverse twice
System.out.println( test + " => " + reverse( test ) + " => " + reverse(reverse( test )) );
// With Numbers
test = "0123456789";
System.out.println( test + " => " + reverse( test ) );
}
}
This is a test => tset a si sihT This is a test => tset a si sihT => This is a test 0123456789 => 9876543210