How do I create a method that accept varargs in Java?

By Wayan in Core API, Lang Package 0 Comment

Varargs (variable arguments) is a new feature in Java 1.5 which allows us to pass multiple values in a single variable name when calling a method. Of course, it can be done easily using array but the varargs add another power to the language.

The varargs can be created by using three periods (...) after the parameter type. If a method accept others parameter than the varargs, the varargs parameter should be the last parameter to the method. And please be aware that overloading a varargs method can make harder to figure out which method is called in the code.

package org.kodejava.lang;

import java.util.Arrays;

public class VarArgsExample {
    public static void main(String[] args) {
        VarArgsExample e = new VarArgsExample();
        e.printParams(1, 2, 3);
        e.printParams(10, 20, 30, 40, 50);
        e.printParams(100, 200, 300, 400, 500);
    }

    public void printParams(int... numbers) {
        System.out.println(Arrays.toString(numbers));
    }
}

Running the code snippet give you the following output:

[1, 2, 3]
[10, 20, 30, 40, 50]
[100, 200, 300, 400, 500]

How do I copy char array to string?

By Wayan in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class CharArrayCopyExample {
    public static void main(String[] args) {
        char[] data = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};

        // Copy all value in the char array and create a new string out of it.
        String text = String.valueOf(data);
        System.out.println(text);

        // Copy a sub array from the char array and create a new string. The
        // following line will just copy 5 characters starting from array index
        // of 3. If the element copied is outside the array index an
        // IndexOutOfBoundsException will be thrown.
        text = String.copyValueOf(data, 3, 5);
        System.out.println(text);
    }
}

The result:

abcdefghij
defgh

How do I shuffle elements of an array?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ArrayShuffle {
    public static void main(String[] args) {
        // Initialize the contents of our array
        String[] alphabets = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J"};

        // As the Collections.shuffle() method need a list for the parameter
        // we convert our array into List using the Arrays class.
        List<String> list = Arrays.asList(alphabets);

        // Here we just simply used the shuffle method of Collections class
        // to shuffle out defined array.
        Collections.shuffle(list);

        // Run the code again and again, then you'll see how simple we do
        // shuffling
        for (String alpha : list) {
            System.out.print(alpha + " ");
        }
    }
}

An example of the generated results are:

F H E A B I G J D C

How do I use for-each in Java?

By Wayan in Core API, Lang Package 0 Comment

Using for-each command to iterate arrays or a list can simplified our code. Below is an example how to do it in Java. The first loop is for iterating array and the second for iterating a list containing a some names.

package org.kodejava.lang;

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

public class ForEachExample {
    public static void main(String[] args) {
        Integer[] numbers = {10, 100, 1000, 10000, 100000, 1000000};

        for (Integer i : numbers) {
            System.out.println("Number: " + i);
        }

        List<String> names = new ArrayList<>();
        names.add("Musk");
        names.add("Nakamoto");
        names.add("Einstein");

        for (String name : names) {
            System.out.println("Name: " + name);
        }
    }
}

The result of the code snippet:

Number: 10
Number: 100
Number: 1000
Number: 10000
Number: 100000
Number: 1000000
Name: Musk
Name: Nakamoto
Name: Einstein

How do I know the minimum and maximum number in an array?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.Arrays;
import java.util.Collections;

public class ArrayMinMax {
    public static void main(String[] args) {
        // Creates an array of integer numbers in it.
        Integer[] numbers = {8, 2, 6, 7, 0, 1, 4, 9, 5, 3};

        // To get the minimum or maximum value from the array we can
        // use the Collections.min() and Collections.max() methods.
        // But as this method requires a list type of data we need
        // to convert the array to list first.
        int min = Collections.min(Arrays.asList(numbers));
        int max = Collections.max(Arrays.asList(numbers));

        // Viola! we get the minimum and the maximum value from the
        // array.
        System.out.println("Min number: " + min);
        System.out.println("Max number: " + max);
    }
}

And here are the results:

Min number: 0
Max number: 9