I will have to skip these tasks until they explain regex.

Question about the task

Replacing numbers

Java Core, Level 9, Lesson 11

Under discussion

1. In a static block, initialize map with (number, word) pairs from 0 to 12 inclusive.
For example, (0, "zero"), (1, "one"), (2, "two")
2. Read the file name from the console, and then read the contents of the file.
3. Use map to replace all of the numbers with words.
4. Display the result.
5. Close the streams.

Example file data:
This costs 1 dollar, but this is 12. The variable is called file1. 110 is a number.

Example console output:
This costs one dollar, but this is twelve. The variable is called file1. 110 is a number.

Requirements:

The Solution class must have a public static Map<Integer, String> field called words that is initialized immediately.
The program must read the file name from the console (use BufferedReader).
The BufferedReader used for reading input from the console must be closed after use.
The program must read the file's contents (use FileReader).
The file input stream (FileReader) must be closed.
The program should write all of the lines from the file to the console, but any numbers must be replaced with the corresponding words in map.
The Solution class must have a static block that adds thirteen pairs to map.

package com.codegym.task.task19.task1924; import java.util.HashMap; import java.util.Map; import java.io.*; /* Replacing numbers */ public class Solution { public static Map<Integer, String> map = new HashMap<Integer, String>(); static { map.put(0, "zero"); map.put(1, "one"); map.put(2, "two"); map.put(3, "three"); map.put(4, "four"); map.put(5, "five"); map.put(6, "six"); map.put(7, "seven"); map.put(8, "eight"); map.put(9, "nine"); map.put(10, "ten"); map.put(11, "eleven"); map.put(12, "twelve"); } public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); FileReader fileReader = new FileReader(reader.readLine()); BufferedReader bufer = new BufferedReader(fileReader); reader.close(); String line; while((line = bufer.readLine()) != null) { for (Map.Entry<Integer, String> par : map.entrySet()) { line = line.replaceAll("\b" + par.getKey() + "\b", par.getValue()); System.out.println(line); } } fileReader.close(); bufer.close(); } }

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Thomas

Level 41 , Bayreuth, Germany

4 December 2023, 08:08

There's absolutely no need to use regex here (or in a lot of the other tasks). Regex may be convenient and save you from writing a lot of code. However not using regex forces you to train your coding skills. That may be a reason why there's (a short) regex introduction in the collections quest.

public static String[] splitAtPunctAndSpace(String s) {
    if (s == null || s.isEmpty()) {
        return new String[0];
    }

    // just took the most plausible but there are more punct characters eg. !"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~
    char[] punct = new char[] {' ', '!', '.', ',', '!', '?', ';', ':'};

    List<String> parts = new ArrayList<>();
    StringBuilder sb = new StringBuilder();

    for (int pos = 0; pos < s.length(); pos++) {
        char c = s.charAt(pos);
        if (contains(punct, c)) {
            parts.add(sb.toString());
            parts.add(String.valueOf(c));
            sb.setLength(0);
        } else if (pos == s.length() - 1) {
            parts.add(sb.append(c).toString());
        } else {
            sb.append(c);
        }
    }
    return parts.toArray(new String[0]);
}

private static boolean contains(char[] haystack, char needle) {
    for (char c : haystack)
        if (c == needle)
            return true;
    return false;
}

This will create an array from a string. All words are in single elements as well as numbers and punct charactes (the ones I declared being punct). That's not pretty code but I just used the minimum necessary. You even could drop the list and the stringBuilder (but that would get rather inconvenient). In the end this is just a few loops and comparisons. In a next step you go through the created array and look at each element if it is a number. Use regex, the Integer class or whatever you like. But you won't need tha

Thomas

Level 41 , Bayreuth, Germany

4 December 2023, 08:10

just look at each char, if it is not 0 - 9, then it is no number and you continue with the next

private static void markNumbers(String[] arr) {
    // todo: check null, empty
    for (int i = 0; i < arr.length; i++) {
        String current = arr[i];
        if (current.isEmpty()) {
            continue;
        }

        boolean isNumber = true;
        for (char c : current.toCharArray()) {
            if (c < '0' || c > '9') {
                isNumber = false;
                break;
            }
        }
        if (isNumber) {
            arr[i] = current + "[NUM]";
        }
    }
}

a little main method for testing

public static void main(String[] args) throws ParseException {
    String data = "1 2 3, that were some numbers. One :100: more. The end?";

    String[] parts = splitAtPunctAndSpace(data);
    markNumbers(parts);

    System.out.println(String.join("", parts));
}

And if you think you need something or if you like to know something then better not wait for codegym to serve it to you. These 4 quests just give you a base.