How do I convert collection to ArrayList?

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

import java.util.ArrayList;
import java.util.LinkedList;

public class CollectionToArrayList {
    public static void main(String[] args) {
        // We create LinkedList collection type at put some values
        // in it. Here we put A, B, C and D letter into it.
        LinkedList<String> linkedList = new LinkedList<>();
        linkedList.push("A");
        linkedList.push("B");
        linkedList.push("C");
        linkedList.push("D");

        // Let say you want to convert it to other type of collection,
        // for instance here we convert it into ArrayList. To do it
        // we can pass the collection created above as a parameter to
        // ArrayList constructor.
        ArrayList<String> arrayList = new ArrayList<>(linkedList);

        // Now we have converted the collection into ArrayList and
        // printed what is inside.
        for (String s : arrayList) {
            System.out.println("s = " + s);
        }
    }
}

How do I convert a collection object into an array?

By Wayan in Core API, Util Package 0 Comment

To convert collection-based object into an array we can use toArray() or toArray(T[] a) method provided by the implementation of Collection interface such as java.util.ArrayList.

package org.kodejava.util;

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

public class CollectionToArrayExample {
    public static void main(String[] args) {
        List<String> words = new ArrayList<>();
        words.add("Kode");
        words.add("Java");
        words.add("-");
        words.add("Learn");
        words.add("Java");
        words.add("by");
        words.add("Examples");

        String[] array = words.toArray(new String[0]);
        for (String word : array) {
            System.out.println(word);
        }
    }
}

Our code snippet result is shown below:

Kode
Java
-
Learn
Java
by
Examples

How do I know if an ArrayList contains a specified item?

By Wayan in Core API, Util Package 2 Comments

In this example we are going to learn how to find out if an ArrayList object contains the specified element. To check if an ArrayList object contains the specified element we can use the contains(Object o) method. This method returns a boolean true when the specified element is found in the ArrayList, otherwise return false. The method returns true if and only if the list contains at least one element, where the element equals to the item in the list.

Let’s see the code snippet below to demonstrate it.

package org.kodejava.util;

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

public class ArrayListContainsExample {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add("Item 1");
        list.add("Item 2");
        list.add("Item 3");
        list.add("Item 4");

        // Check to see if the list contains "Item 1".
        String itemToFind = "Item 1";
        System.out.println("contains(" + itemToFind + "): " + list.contains(itemToFind));

        // Check to see if the list contains "Item 20".
        itemToFind = "Item 20";
        System.out.println("contains(" + itemToFind + "): " + list.contains(itemToFind));
    }
}

The output of the code snippet above are:

contains(Item 1): true
contains(Item 20): false