How do I align string print out in left, right, center alignment?

By Wayan in Core API, Lang Package 1 Comment

The following code snippet will teach you how to align string in left, right or center alignment when you want to print out string to a console. We will print the string using the printf(String format, Object... args) method. The format specifier / parameter defines how the string will be formatted for output and the args is the value that will be formatted.

The format parameter / specifier include flags, width, precision and conversion-characters in the order shown below. The square brackets in the notation means the part is an optional parameter.

% [flags] [width] [.precision] conversion-character
Flags Description
- left-align the output, when not specified the default is to right-align
+ print (+) or (-) sign for numeric value
0 zero padded a numeric value
, comma grouping separator for number greater that 1000
space will output a (-) symbol for negative value and a space if positive
Conversion Description
s string, use capital S to uppercase the strings
c character, use capital C to uppercase the characters
d integer: byte, short, integer, long
f floating point number: float, double
n new line

Width: Defines the field width for printing out the value of argument. It also represents the minimum number of characters to
be printed out to the output.

Precision: For floating-point conversion the precision define the number of digits of precision in a floating point value. For string value this will extract the substring.

To center the string for output we use the StringUtils.center() method from the Apache Commons Lang library. This method will center-align the string str in a larger string of size using the default space character (‘ ‘). You can supply the third parameter to define your own space character / string.

package org.kodejava.lang;

import org.apache.commons.lang3.StringUtils;

import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.ChronoUnit;

public class StringAlignment {
    private static final Object[][] people = {
            {"Alice", LocalDate.of(2000, Month.JANUARY, 1)},
            {"Bob", LocalDate.of(1989, Month.DECEMBER, 15)},
            {"Carol", LocalDate.of(1992, Month.JULY, 24)},
            {"Ted", LocalDate.of(2006, Month.MARCH, 13)},
    };

    public static void main(String[] args) {
        String nameFormat = "| %1$-20s | ";
        String dateFormat = " %2$tb %2$td, %2$tY  | ";
        String ageFormat = " %3$3s |%n";
        String format = nameFormat.concat(dateFormat).concat(ageFormat);
        String line = new String(new char[48]).replace('\0', '-');

        System.out.println(line);
        System.out.printf("|%s|%s|%s|%n",
                StringUtils.center("Name", 22),
                StringUtils.center("Birth Date", 16),
                StringUtils.center("Age", 6));
        System.out.println(line);

        for (Object[] data : people) {
            System.out.printf(format,
                    data[0], data[1],
                    ChronoUnit.YEARS.between((LocalDate) data[1], LocalDate.now()));
        }

        System.out.println(line);
    }
}

Here is the output of our code snippet above:

------------------------------------------------
|         Name         |   Birth Date   | Age  |
------------------------------------------------
| Alice                |  Jan 01, 2000  |   17 |
| Bob                  |  Dec 15, 1989  |   27 |
| Carol                |  Jul 24, 1992  |   24 |
| Ted                  |  Mar 13, 2006  |   10 |
------------------------------------------------

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=org/apache/commons/commons-lang3/3.12.0/commons-lang3-3.12.0.jar -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central

How do I find text between two strings?

By Wayan in Apache Commons, Commons Lang 2 Comments

In this example we’ll use the StringUtils.substringBetween() method. Here we’ll extract the title and body of our HTML document. Let’s see the code.

package org.kodejava.commons.lang;

import java.util.Date;

import org.apache.commons.lang3.StringUtils;

public class NestedString {
    public static void main(String[] args) {
        String helloHtml = "<html>" +
                "<head>" +
                "   <title>Hello World from Java</title>" +
                "<body>" +
                "Hello, today is: " + new Date() +
                "</body>" +
                "</html>";

        String title = StringUtils.substringBetween(helloHtml, "<title>", "</title>");
        String content = StringUtils.substringBetween(helloHtml, "<body>", "</body>");

        System.out.println("title = " + title);
        System.out.println("content = " + content);
    }
}

By print out the title and content we’ll see something similar to:

title = Hello World from Java
content = Hello, today is: Thu Sep 30 06:32:32 CST 2021

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central

How do I check for an empty string?

By Wayan in Apache Commons, Commons Lang 1 Comment

StringUtils.isBlank() method check to see is the string contains only whitespace characters, empty or has a null value. If these conditions are true the strings are considered blank.

There’s also a StringUtils.isEmpty(), only this method doesn’t check for whitespaces-only string. For checking the opposite condition there are StringUtils.isNotBlank() and StringUtils.isNotEmpty().

Using these methods we can avoid repeating the code for checking empty string which can include more code to type then using these handy methods.

package org.kodejava.commons.lang;

import org.apache.commons.lang3.StringUtils;

public class CheckEmptyString {
    public static void main(String[] args) {
        String var1 = null;
        String var2 = "";
        String var3 = "    \t\t\t";
        String var4 = "Hello World";

        System.out.println("var1 is blank? = " + StringUtils.isBlank(var1));
        System.out.println("var2 is blank? = " + StringUtils.isBlank(var2));
        System.out.println("var3 is blank? = " + StringUtils.isBlank(var3));
        System.out.println("var4 is blank? = " + StringUtils.isBlank(var4));

        System.out.println("var1 is not blank? = " + StringUtils.isNotBlank(var1));
        System.out.println("var2 is not blank? = " + StringUtils.isNotBlank(var2));
        System.out.println("var3 is not blank? = " + StringUtils.isNotBlank(var3));
        System.out.println("var4 is not blank? = " + StringUtils.isNotBlank(var4));

        System.out.println("var1 is empty? = " + StringUtils.isEmpty(var1));
        System.out.println("var2 is empty? = " + StringUtils.isEmpty(var2));
        System.out.println("var3 is empty? = " + StringUtils.isEmpty(var3));
        System.out.println("var4 is empty? = " + StringUtils.isEmpty(var4));

        System.out.println("var1 is not empty? = " + StringUtils.isNotEmpty(var1));
        System.out.println("var2 is not empty? = " + StringUtils.isNotEmpty(var2));
        System.out.println("var3 is not empty? = " + StringUtils.isNotEmpty(var3));
        System.out.println("var4 is not empty? = " + StringUtils.isNotEmpty(var4));
    }
}

The result of our program are:

var1 is blank? = true
var2 is blank? = true
var3 is blank? = true
var4 is blank? = false
var1 is not blank? = false
var2 is not blank? = false
var3 is not blank? = false
var4 is not blank? = true
var1 is empty? = true
var2 is empty? = true
var3 is empty? = false
var4 is empty? = false
var1 is not empty? = false
var2 is not empty? = false
var3 is not empty? = true
var4 is not empty? = true

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central

How do I count word occurrences in a string?

By Wayan in Apache Commons, Commons Lang 0 Comment 
package org.kodejava.commons.lang;

import org.apache.commons.lang3.StringUtils;

public class WordCountDemo {
    public static void main(String[] args) {
        // We have the source text we'll do the search on.
        String source = "From the download page, you can download the Java " +
            "Tutorials for browsing offline. Or you can just download " +
            "the example.";
        // The word we want to count its occurrences
        String word = "you";

        // Using StringUtils.countMatches() method we can count the occurrences
        // frequency of a word/letter in the giver source of string.
        int wordFound = StringUtils.countMatches(source, word);

        // Print how many we have found the word
        System.out.println(wordFound + " occurrences of the word '" + word +
            "' was found in the text.");
    }
}

Here is the result of the code above.

2 occurrences of the word 'you' was found in the text.

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central

How do I reverse a string, words or sentences?

By Wayan in Apache Commons, Commons Lang 0 Comment 
package org.kodejava.commons.lang;

import org.apache.commons.lang3.StringUtils;

public class StringReverseDemo {
    public static void main(String[] args) {
        // We have an original string here that we'll need to reverse.
        String words = "The quick brown fox jumps over the lazy dog";

        // Using StringUtils.reverse we can reverse the string letter by letter.
        String reversed = StringUtils.reverse(words);

        // Now we want to reverse per word, we can use
        // StringUtils.reverseDelimited() method to do this.
        String delimitedReverse = StringUtils.reverseDelimited(words, ' ');

        // Print out the result
        System.out.println("Original: " + words);
        System.out.println("Reversed: " + reversed);
        System.out.println("Delimited Reverse: " + delimitedReverse);
    }
}

Here is the result:

Original: The quick brown fox jumps over the lazy dog
Reversed: god yzal eht revo spmuj xof nworb kciuq ehT
Delimited Reverse: dog lazy the over jumps fox brown quick The

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central

How do I check if a string is empty or not?

By Wayan in Apache Commons, Commons Lang 0 Comment 
package org.kodejava.commons.lang;

import org.apache.commons.lang3.StringUtils;

public class EmptyStringCheckDemo {
    public static void main(String[] args) {
        // Create some variable to hold some string that empty, contains only
        // white spaces and words.
        String one = "";
        String two = "\t\r\n";
        String three = "     ";
        String four = null;
        String five = "four four two";

        // We can use StringUtils class for checking if a string is empty or not
        // using StringUtils.isBlank() method. This method will return true if
        // the tested string is empty, contains white space only or null.
        System.out.println("Is one empty? " + StringUtils.isBlank(one));
        System.out.println("Is two empty? " + StringUtils.isBlank(two));
        System.out.println("Is three empty? " + StringUtils.isBlank(three));
        System.out.println("Is four empty? " + StringUtils.isBlank(four));
        System.out.println("Is five empty? " + StringUtils.isBlank(five));

        // On the other side, the StringUtils.isNotBlank() methods complement
        // the previous method. It will check is a tested string is not empty.
        System.out.println("Is one not empty? " + StringUtils.isNotBlank(one));
        System.out.println("Is two not empty? " + StringUtils.isNotBlank(two));
        System.out.println("Is three not empty? " + StringUtils.isNotBlank(three));
        System.out.println("Is four not empty? " + StringUtils.isNotBlank(four));
        System.out.println("Is five not empty? " + StringUtils.isNotBlank(five));
    }
}

Here is the result:

Is one empty? true
Is two empty? true
Is three empty? true
Is four empty? true
Is five empty? false
Is one not empty? false
Is two not empty? false
Is three not empty? false
Is four not empty? false
Is five not empty? true

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

Maven Central