How do I generate random string?

By Wayan in Security 0 Comment 
package org.kodejava.security;

import java.security.SecureRandom;
import java.util.Random;

public class RandomString {
    public static final String SOURCES =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

    public static void main(String[] args) {
        RandomString rs = new RandomString();
        System.out.println(rs.generateString(new Random(), SOURCES, 10));
        System.out.println(rs.generateString(new Random(), SOURCES, 10));
        System.out.println(rs.generateString(new SecureRandom(), SOURCES, 15));
        System.out.println(rs.generateString(new SecureRandom(), SOURCES, 15));
    }

    /**
     * Generate a random string.
     *
     * @param random     the random number generator.
     * @param characters the characters for generating string.
     * @param length     the length of the generated string.
     */
    public String generateString(Random random, String characters, int length) {
        char[] text = new char[length];
        for (int i = 0; i < length; i++) {
            text[i] = characters.charAt(random.nextInt(characters.length()));
        }
        return new String(text);
    }
}

Example string produced by the code snippets are:

bJGjSgoy7G
SoeTjBy83s
IolJZtkttJixAVY
ZOvQnICNcwcCdJ8

How to truncate a string after n number of words?

By Wayan in Regex 1 Comment 
package org.kodejava.regex;

public class GetNumberOfWordsFromString {
    public static void main(String[] args) {
        String text = "The quick brown fox jumps over the lazy dog.";

        String one = truncateAfterWords(1, text);
        System.out.println("1 = " + one);

        String two = truncateAfterWords(2, text);
        System.out.println("2 = " + two);

        String four = truncateAfterWords(4, text);
        System.out.println("4 = " + four);

        String six = truncateAfterWords(6, text);
        System.out.println("6 = " + six);
    }

    /**
     * Truncate a string after n number of words.
     *
     * @param words number of words to truncate after.
     * @param text  the text.
     * @return truncated text.
     */
    public static String truncateAfterWords(int words, String text) {
        String regex = String.format("^((?:\\W*\\w+){%s}).*$", words);
        return text.replaceAll(regex, "$1");
    }
}

The result of the snippet:

1 = The
2 = The quick
4 = The quick brown fox
6 = The quick brown fox jumps over

How to remove non ASCII characters from a string?

By Wayan in Regex 0 Comment

The code snippet below remove the characters from a string that is not inside the range of x20 and x7E ASCII code. The regex below strips non-printable and control characters. But it also keeps the linefeed character n (x0A) and the carriage return r (x0D) characters.

package org.kodejava.regex;

public class ReplaceNonAscii {
    public static void main(String[] args) {
        String str = "Thè quïck brøwn føx jumps over the lãzy dôg.";
        System.out.println("str = " + str);

        // Replace all non ascii chars in the string.
        str = str.replaceAll("[^\\x0A\\x0D\\x20-\\x7E]", "");
        System.out.println("str = " + str);
    }
}

Snippet output:

str = Thè quïck brøwn føx jumps over the lãzy dôg.
str = Th quck brwn fx jumps over the lzy dg.

How to split a string by a number of characters?

By Wayan in Core API, Lang Package 1 Comment

The following code snippet will show you how to split a string by numbers of characters. We create a method called splitToNChars() that takes two arguments. The first arguments is the string to be split and the second arguments is the split size.

This splitToNChars() method will split the string in a for loop. First we’ll create a List object that will store parts of the split string. Next we do a loop and get the substring for the defined size from the text and store it into the List. After the entire string is read we convert the List object into an array of String by using the List‘s toArray() method.

Let’s see the code snippet below:

package org.kodejava.lang;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class SplitStringForEveryNChar {
    public static void main(String[] args) {
        String text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        System.out.println(Arrays.toString(splitToNChar(text, 3)));
        System.out.println(Arrays.toString(splitToNChar(text, 4)));
        System.out.println(Arrays.toString(splitToNChar(text, 5)));
    }

    /**
     * Split text into n number of characters.
     *
     * @param text the text to be split.
     * @param size the split size.
     * @return an array of the split text.
     */
    private static String[] splitToNChar(String text, int size) {
        List<String> parts = new ArrayList<>();

        int length = text.length();
        for (int i = 0; i < length; i += size) {
            parts.add(text.substring(i, Math.min(length, i + size)));
        }
        return parts.toArray(new String[0]);
    }
}

When run the code snippet will output:

[ABC, DEF, GHI, JKL, MNO, PQR, STU, VWX, YZ]
[ABCD, EFGH, IJKL, MNOP, QRST, UVWX, YZ]
[ABCDE, FGHIJ, KLMNO, PQRST, UVWXY, Z]

How do I split a string with multiple spaces?

By Wayan in Core API, Lang Package 3 Comments

This code snippet show you how to split string with multiple white-space characters. To split the string this way we use the "\s+" regular expression. The white-space characters include space, tab, line-feed, carriage-return, new line, form-feed.

Let’s see the code snippet below:

package org.kodejava.lang;

import java.util.Arrays;

public class SplitStringMultiSpaces {
    public static void main(String[] args) {
        String text = "04/11/2021    SHOES      RUNNING RED   99.9 USD";

        // Split the string using the \s+ regex to split multi spaces
        // line of text.
        String[] items = text.split("\\s+");
        System.out.println("Length = " + items.length);
        System.out.println("Items  = " + Arrays.toString(items));
    }
}

The result of the code snippet is:

Length = 6
Items  = [04/11/2021, SHOES, RUNNING, RED, 99.9, USD]