How do I remove elements from Deque?

By Wayan in Core API, Util Package 0 Comment

This example shows you how to remove some elements from the Deque object. We can use the following methods for removing elements from Deque: remove(), remove(Object o), removeFirst(), removeLast().

package org.kodejava.util;

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

public class RemoveDequeDemo {
    public static void main(String[] args) {
        Deque<String> deque = new LinkedList<>();
        deque.add("A");
        deque.add("B");
        deque.add("C");
        deque.add("D");
        deque.add("E");
        deque.add("F");

        // Removes and retrieves the head of this Deque
        deque.remove();      // Removes "A"

        // Removes the first occurrence of element from this Deque
        deque.remove("F");   // Removes "F"

        // Retrieves and removes the first element of this deque
        deque.removeFirst(); // Removes "B"

        // Retrieves and removes the last element of this deque
        deque.removeLast();  // Removes "E"

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

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 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

How do I sort LinkedList elements?

By Wayan in Core API, Util Package 0 Comment

To sort the elements of LinkedList we can use the Collections.sort(List<T> list) static methods. The default order of the sorting is a descending order.

package org.kodejava.util;

import java.util.LinkedList;
import java.util.Collections;

public class LinkedListSort {
    public static void main(String[] args) {
        LinkedList<String> grades = new LinkedList<>();
        grades.add("E");
        grades.add("C");
        grades.add("A");
        grades.add("F");
        grades.add("B");
        grades.add("D");

        System.out.println("Before sorting:");
        System.out.println("===============");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }

        // Sort the elements of linked list based on its data
        // natural order.
        Collections.sort(grades);

        System.out.println("After sorting:");
        System.out.println("===============");
        for (String grade : grades) {
            System.out.println("Grade = " + grade);
        }
    }
}

The result of the program are:

Before sorting:
===============
Grade = E
Grade = C
Grade = A
Grade = F
Grade = B
Grade = D
After sorting:
===============
Grade = A
Grade = B
Grade = C
Grade = D
Grade = E
Grade = F

How do I get the first and the last element of a LinkedList?

By Wayan in Core API, Util Package 0 Comment

The get the first element we can use the LinkedList.getFirst() method and to get the last element we can use the LinkedList.getLast() method.

package org.kodejava.util;

import java.util.LinkedList;

public class LinkedListGetFirstLast {
    public static void main(String[] args) {
        LinkedList<String> names = new LinkedList<>();
        names.add("Alice");
        names.add("Bob");
        names.add("Carol");
        names.add("Mallory");

        // Get the first and the last element of the linked list
        String first = names.getFirst();
        String last = names.getLast();

        System.out.println("First member = " + first);
        System.out.println("Last member  = " + last);
    }
}

The program will print the following result:

First member = Alice
Last member  = Mallory