How do I add elements into a Deque?

By Wayan in Core API, Util Package 0 Comment

To add elements into a Deque object we can use the add(), addFirst() and addLast() method call.

package org.kodejava.util;

import java.util.Deque;
import java.util.LinkedList;

public class DequeAddElement {
    public static void main(String[] args) {
        // Create an instance of Deque using LinkedList class.
        Deque<String> deque = new LinkedList<>();

        // Insert a word into the Deque
        deque.add("jumps");

        // Insert words at the beginning of the current Deque
        // elements
        deque.addFirst("fox");
        deque.addFirst("brown");
        deque.addFirst("quick");
        deque.addFirst("The");

        // Insert words at the end of the current Deque elements
        deque.addLast("over");
        deque.addLast("the");
        deque.addLast("lazy");
        deque.addLast("dog");

        for (String word : deque) {
            System.out.println("Word = " + word);
        }
    }
}

Here is the output:

Word = The
Word = quick
Word = brown
Word = fox
Word = jumps
Word = over
Word = the
Word = lazy
Word = dog

How do I create a java.util.Hashtable and iterates its contents?

By Wayan in Core API, Util Package 0 Comment

The code snippet shows you how to create and instance of Hashtable that stores Integer values using a String keys. After that we iterate the elements of the Hashtable using the Enumeration interface.

package org.kodejava.util;

import java.util.Enumeration;
import java.util.Hashtable;

public class HashtableDemo {
    public static void main(String[] args) {
        // Creates an instance of Hashtable
        Hashtable<String, Integer> numbers = new Hashtable<>();
        numbers.put("one", 1);
        numbers.put("two", 2);
        numbers.put("three", 3);

        // Returns an enumeration of the keys in this Hashtable
        Enumeration<String> keys = numbers.keys();
        while (keys.hasMoreElements()) {
            // Returns the next element of this enumeration if this
            // enumeration object has at least one more element to
            // provide
            String key = keys.nextElement();
            System.out.printf("Key: %s, Value: %d%n", key, numbers.get(key));
        }
    }
}

How do I create Deque using ArrayDeque class?

By Wayan in Core API, Util Package 0 Comment

This example show you how to create a Deque using the ArrayDeque implementation. The ArrayDeque stores its elements using an array. If the number of elements exceeds the space in the array, a new array will be allocated, and all elements moved the new allocated array.

In the code below we initiate the size of the Deque to store five elements. When we add the element number six the array that stores the elements of the Deque will be resized.

package org.kodejava.util;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
    public static void main(String[] args) {
        // Constructs an empty array deque with an initial capacity
        // sufficient to hold the specified number of elements.
        Deque<Integer> deque = new ArrayDeque<>(5);
        deque.add(1);
        deque.add(1);
        deque.add(2);
        deque.add(3);
        deque.add(5);
        deque.add(8);
        deque.add(14);
        deque.add(22);

        for (Integer number : deque) {
            System.out.println("Number = " + number);
        }
    }
}

How do I read java.util.Vector object using java.util.Enumeration?

By Wayan in Core API, Util Package 0 Comment

The following code snippets show you how to iterate and read java.util.Vector elements using the java.util.Enumeration.

package org.kodejava.util;

import java.util.Enumeration;
import java.util.Vector;

public class VectorEnumeration {

    public static void main(String[] args) {
        Vector<String> data = new Vector<>();
        data.add("one");
        data.add("two");
        data.add("three");

        StringBuilder sb = new StringBuilder("Data: ");

        // Iterates vector object to read it elements
        for (Enumeration<String> enumeration = data.elements();
             enumeration.hasMoreElements(); ) {
            sb.append(enumeration.nextElement()).append(",");
        }

        // Delete the last ","
        sb.deleteCharAt(sb.length() - 1);
        System.out.println(sb);
    }
}

How do I remove the first or the last found element from Deque?

By Wayan in Core API, Util Package 0 Comment

This example demonstrates the use of Deque.removeFirstOccurrence() method call to remove the first occurrences of an element in the Deque object and Deque.removeLastOccurrence() method call to remove the last occurrences of an element in the Deque object.

package org.kodejava.util;

import java.util.Deque;
import java.util.Iterator;
import java.util.LinkedList;

public class DequeRemoveDemo {
    public static void main(String[] args) {
        Deque<String> deque1 = new LinkedList<>();
        deque1.offer("a");
        deque1.offer("b");
        deque1.offer("c");
        deque1.offer("d");
        deque1.offer("e");
        deque1.offer("d");

        Deque<String> deque2 = new LinkedList<>(deque1);

        // Removes the first occurrence of letter "d" from deque1
        deque1.removeFirstOccurrence("d");

        Iterator<String> first = deque1.iterator();
        System.out.println("After removeFirstOccurrence(Object o): ");
        System.out.println("=======================================");
        while (first.hasNext()) {
            System.out.println(first.next());
        }

        // Removes the last occurrence of letter "d" from deque2
        deque2.removeLastOccurrence("d");
        Iterator<String> last = deque2.iterator();
        System.out.println("After removeLastOccurrence(Object o): ");
        System.out.println("========================================");
        while (last.hasNext()) {
            System.out.println(last.next());
        }
    }
}

The output of the code snippet above is:

After removeFirstOccurrence(Object o): 
=======================================
a
b
c
e
d
After removeLastOccurrence(Object o): 
========================================
a
b
c
d
e