Wednesday, 14 December 2016

Chapter 12 Exercise 27, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

12.27 (Replace words)
Suppose you have a lot of files in a directory that contain words Exercisei_j,
where i and j are digits. Write a program that pads a 0 before i if i is a
single digit and 0 before j if j is a single digit. For example, the word Exercise2_1
in a file will be replaced by Exercise02_01. In Java, when you pass the symbol *
from the command line, it refers to all files in the directory (see Supplement III.V).

public class Exercise_27 {

    public static void main(String[] args) {

        if (args.length == 0) {
            System.out.println("Invalid Arguments.");
            System.out.println("Usage: java Chapter_12.Exercise_27");
        for (String s : args) {

            if (s.matches("Exercise[\\d]_[\\d].*")) {
                StringBuilder sb = new StringBuilder(s);
                sb.insert(s.indexOf('_') - 1, "0");
                sb.insert(s.indexOf('_') + 2, "0");
                new File(s).renameTo(new File(sb.toString()));



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