Java Programming
I would like to know how the toString is being called from the constructor in the following code.Any feedback would help me to improve my understanding of java concepts.
***************************************************************************************
// CharSequenceDemo presents a String value -- backwards.
public class CharSequenceDemo implements CharSequence {
private String s;
public CharSequenceDemo(String s) {
//It would be much more efficient to just reverse the string
//in the constructor. But a lot less fun!
this.s = s;
}
//If the string is backwards, the end is the beginning!
private int fromEnd(int i) {
return s.length() - 1 - i;
}
public char charAt(int i) {
if ((i < 0) || (i >= s.length())) {
throw new StringIndexOutOfBoundsException(i);
}
return s.charAt(fromEnd(i));
}
public int length() {
return s.length();
}
public CharSequence subSequence(int start, int end) {
if (start < 0) {
throw new StringIndexOutOfBoundsException(start);
}
if (end > s.length()) {
throw new StringIndexOutOfBoundsException(end);
}
if (start > end) {
throw new StringIndexOutOfBoundsException(start - end);
}
StringBuilder sub =
new StringBuilder(s.subSequence(fromEnd(end), fromEnd(start)));
return sub.reverse();
}
public String toString() {
StringBuilder s = new StringBuilder(this.s);
return s.reverse().toString();
}
//Random int from 0 to max.
private static int random(int max) {
return (int) Math.round(Math.random() * max + 0.5);
}
public static void main(String[] args) {
CharSequenceDemo s =
new CharSequenceDemo("Write a class that implements the CharSequence interface found in the java.lang package.");
//exercise charAt() and length()
for (int i = 0; i < s.length(); i++) {
System.out.println(s.charAt(i));
}
//exercise subSequence() and length();
int start = random(s.length() - 1);
int end = random(s.length() - 1 - start) + start;
System.out.println(s.subSequence(start, end));
//exercise toString();
System.out.println(s);
}
}
***************************************************************************************
