How do I iterate LinkedList elements using ListIterator?

By Wayan in Core API, Util Package 0 Comment

This example show you how to use the ListIterator interface to iterate elements of a LinkedList.

package org.kodejava.util;

import java.util.List;
import java.util.LinkedList;
import java.util.ListIterator;

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

        // Retrieves object from LinkedList using the ListIterator
        // interface.
        ListIterator<String> iterator = grades.listIterator();
        while (iterator.hasNext()) {
            System.out.println("Grades: " + iterator.next());
            System.out.println("  hasPrevious  : " + iterator.hasPrevious());
            System.out.println("  hasNext      : " + iterator.hasNext());
            System.out.println("  previousIndex: " + iterator.previousIndex());
            System.out.println("  nextIndex    : " + iterator.nextIndex());
        }
    }
}

The program will print the following output:

Grades: A
  hasPrevious  : true
  hasNext      : true
  previousIndex: 0
  nextIndex    : 1
Grades: B
  hasPrevious  : true
  hasNext      : true
  previousIndex: 1
  nextIndex    : 2
Grades: C
  hasPrevious  : true
  hasNext      : true
  previousIndex: 2
  nextIndex    : 3
Grades: D
  hasPrevious  : true
  hasNext      : true
  previousIndex: 3
  nextIndex    : 4
Grades: E
  hasPrevious  : true
  hasNext      : false
  previousIndex: 4
  nextIndex    : 5

How do I iterate LinkedList elements using Iterator?

By Wayan in Core API, Util Package 0 Comment

This example show you how to use the Iterator interface to iterate elements of a LinkedList.

package org.kodejava.util;

import java.util.List;
import java.util.LinkedList;
import java.util.Iterator;

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

        // Iterates elements in LinkedList using Iterator.
        Iterator<String> iterator = grades.iterator();
        while (iterator.hasNext()) {
            System.out.println("Grade: " + iterator.next());
        }
    }
}

This program prints the following output:

Grade: A
Grade: B
Grade: C
Grade: D
Grade: E

How do I create a LinkedList?

By Wayan in Core API, Util Package 0 Comment

A linked list is a fundamental data structure in programming. It can store data and a references to the next and/or to the previous node. There can be a singly linked list, a doubly linked list and a circularly linked list.

The code below show you how to use the java.util.LinkedList class to create a linked list. In the example we create a LinkedList to store a string object using the add(Object o) method. After create the list we iterate the list and print out the contents.

package org.kodejava.util;

import java.util.List;
import java.util.LinkedList;

public class LinkedListCreate {
    public static void main(String[] args) {
        // Creates a new instance of java.util.LinkedList and
        // adds five string object into the list.
        List<String> grades = new LinkedList<>();
        grades.add("A");
        grades.add("B");
        grades.add("C");
        grades.add("E");
        grades.add("F");

        // Iterates the LinkedList object using the for each
        // statement.
        for (String grade : grades) {
            System.out.println("Grade: " + grade);
        }
    }
}

This program will produce the following output:

Grade: A
Grade: B
Grade: C
Grade: E
Grade: F

How do I convert java.util.Set into Array?

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

import java.util.*;

public class SetToArray {
    public static void main(String[] args) {
        // Create a java.util.Set object and add some integers into the Set.
        Set<Integer> numberSet = new HashSet<>();
        numberSet.add(1);
        numberSet.add(2);
        numberSet.add(3);
        numberSet.add(5);
        numberSet.add(8);

        // Converting a java.util.Set into an array can be done by creating a
        // java.util.List object from the Set and then convert it into an array
        // by calling the toArray() method on the list object.
        List<Integer> numberList = new ArrayList<>(numberSet);
        Integer[] numbers = numberList.toArray(new Integer[0]);

        // Display the content of numbers array.
        for (int i = 0; i < numbers.length; i++) {
            Integer number = numbers[i];
            System.out.print(number + (i < numbers.length - 1 ? ", " : "\n"));
        }

        // Display the content of numbers array using the for-each loop.
        for (Integer number : numbers) {
            System.out.print(number + ", ");
        }
    }
}

How do I convert Set into List?

By Wayan in Core API, Util Package 0 Comment

The code below gives you an example of converting a java.util.Set into a java.util.List. It has simply done by creating a new instance of List and pass the Set as the argument of the constructor.

package org.kodejava.util;

import java.util.*;

public class SetToList {
    public static void main(String[] args) {
        // Create a Set and add some objects into the Set.
        Set<Object> set = new HashSet<>();
        set.add("A");
        set.add(10L);
        set.add(new Date());

        // Convert the Set to a List can be done by passing the Set instance into
        // the constructor of a List implementation class such as ArrayList.
        List<Object> list = new ArrayList<>(set);
        for (Object o : list) {
            System.out.println("Object = " + o);
        }
    }
}

The output of the code snippet are:

Object = A
Object = 10
Object = Mon Oct 04 20:20:26 CST 2021