JAVA

how to make an arraylist java

ArrayList<Integer> integerArray = new ArrayList<Integer>();
ArrayList<String> stringArray = new ArrayList<String>();
ArrayList<Double> doubleArray = new ArrayList<Double>();
//... keep replacing what is inside the <> with the appropriate
//data type

how to make an array of arraylists in java

ArrayList<Integer> [] myList = (ArrayList<Integer>[]) new ArrayList[4];

java create arraylist

//dont forget to import ArrayList--> import java.util.ArrayList;

ArrayList<String> yourListName = new ArrayList<String>();
        yourListName.add("Ace");
        yourListName.add("Two");
        yourListName.add("Three");
        yourListName.add("J");
        yourListName.add("Q");
        
        //display list
        for (String s : yourListName) {
            System.out.println(s);
        }

own arraylist in java

//Step 1 : Define CustomList interfaces

public interface CustomList<E> extends Iterable<E> {

    boolean isEmpty();

    int size();

    boolean add(E element);

    boolean add(int index, E element);

    void remove(E element);

    E get(int index);

    int indexOf(E element);

    void set(int index, E element);

    boolean contains(E element);

    void clear();

    E[] toArray();
}

//Step2 : Implementation

package com.spacex.data.structure.list;

import java.util.Arrays;
import java.util.Iterator;

public class CustomArrayList<E> implements CustomList<E> {

    private E[] elements;
    private int size;

    public CustomArrayList() {
        this(10);
    }

    public CustomArrayList(int initSize) {
        if (initSize < 0) {
            throw new IllegalArgumentException("illegal size:" + initSize);
        }
        this.elements = (E[]) new Object[initSize];
    }

    @Override
    public boolean isEmpty() {
        return size() == 0;
    }

    @Override
    public int size() {
        return this.size;
    }

    private void ensureCapacity(int needCapacity) {
        if (needCapacity > elements.length) {
            Object[] oldElements = this.elements;
            int newSize = this.size * 2 + 1;
            this.elements = (E[]) new Object[newSize];
            this.elements = (E[]) Arrays.copyOf(oldElements, newSize);
        }
    }

    @Override
    public boolean add(E element) {
        ensureCapacity(this.size + 1);
        elements[this.size++] = element;
        return true;
    }

    private void checkRange(int index) {
        if (index < 0 || index >= (this.size + 1)) {
            throw new IllegalArgumentException("illegal index:" + index);
        }
    }

    @Override
    public boolean add(int index, E element) {
        checkRange(index);
        ensureCapacity(this.size + 1);
        System.arraycopy(this.elements, index, elements, index + 1, size - index);
        elements[index] = element;
        this.size++;
        return true;
    }

    @Override
    public void remove(E element) {
        if (element == null) {
            for (int i = 0; i < this.size; i++) {
                if (this.elements[i] == null) {
                    fastRemove(i);
                    return;
                }
            }
        } else {
            for (int i = 0; i < this.size; i++) {
                if (element.equals(this.elements[i])) {
                    fastRemove(i);
                    return;
                }
            }
        }
    }

    private void fastRemove(int index) {
        int movedNumber = this.size - index - 1;
        if (movedNumber > 0) {
            System.arraycopy(this.elements, index + 1, this.elements, index, movedNumber);
        }
        this.elements[--this.size] = null;
    }

    @Override
    public E get(int index) {
        E e = this.elements[index];
        return e;
    }

    @Override
    public int indexOf(E element) {

        if (element == null) {
            for (int i = 0; i < this.elements.length; i++) {
                if (this.elements[i] == null) {
                    return i;
                }
            }
        } else {
            for (int i = 0; i < this.elements.length; i++) {
                if (element.equals(this.elements[i])) {
                    return i;
                }
            }
        }
        return -1;
    }

    @Override
    public void set(int index, E element) {
        checkRange(index);
        ensureCapacity(this.size + 1);
        this.elements[index] = element;
    }

    @Override
    public boolean contains(E element) {
        if (element == null) {
            for (E e : this.elements) {
                if (e == null) {
                    return true;
                }
            }
        } else {
            for (E e : this.elements) {
                if (element.equals(e)) {
                    return true;
                }
            }
        }

        return false;
    }

    @Override
    public void clear() {
        for (int i = 0; i < this.size; i++) {
            this.elements[i] = null;
        }
        this.size = 0;
    }

    @Override
    public E[] toArray() {
        return this.elements;
    }

    @Override
    public Iterator<E> iterator() {
        return new CustomIterator<>();
    }

    @Override
    public String toString() {
        return "CustomArrayList{" +
                "elements=" + Arrays.toString(elements) +
                ", size=" + size +
                '}';
    }

    private class CustomIterator<E> implements Iterator<E> {

        private int current = 0;

        @Override
        public boolean hasNext() {
            return this.current < size();
        }

        @Override
        public E next() {
            E value = (E) elements[current++];
            return value;
        }
    }
}

java how to create arraylist

import java.util.ArrayList;
//create ArrayList
ArrayList<String> arrayList = new ArrayList<String>();

Java Create ArrayList in Java

import java.util.ArrayList;

class Main {
  public static void main(String[] args){

    // create ArrayList
    ArrayList<String> languages = new ArrayList<>();

    // Add elements to ArrayList
    languages.add("Java");
    languages.add("Python");
    languages.add("Swift");
    System.out.println("ArrayList: " + languages);
  }
}

how to make a new arraylist java

ArrayList<Type> name = new ArrayList<Type>();

Syntax of how to create ArrayList in Java

ArrayList<Type> arrayList= new ArrayList<>();

creating an array list in java

ArrayList<String> al = new ArrayList<String>();

how to create Java ArrayList

// welcome to softhunt.net
import java.util.ArrayList;

class Main {
  public static void main(String[] args){

    // create ArrayList
    ArrayList<String> Websites = new ArrayList<>();

    // Add elements to ArrayList
    Websites.add("Softhunt.net");
    Websites.add("Pythonprogramming.com");
    Websites.add("Tutorial.io");
    System.out.println("ArrayList: " + Websites);
  }
}

How to create an ArrayList

ArrayList<Integer> list=new ArrayList<Integer>();

java make arraylist

//Create the Arraylist variable: . Replace the T with the type of 
//data to be stored in the list.
ArrayList<T> exampleList = new ArrayList<>();
//You can now perform operations on this ArrayList

Java Creating an ArrayList

// create Integer type arraylist
ArrayList<Integer> arrayList = new ArrayList<>();

// create String type arraylist
ArrayList<String> arrayList = new ArrayList<>();

how to declare array of arraylist in java

List<List<Individual>> group = new ArrayList<List<Individual>>(4);

how to create arraylist in java

import java.util.ArrayList;
public class ArrayLists {
    public static void main(String[] args) {

        ArrayList<String> cars = new ArrayList<String>();

        cars.add("Volvo");
        cars.add("BMW");
        cars.add("Ford");
        cars.add("Mazda");

        System.out.println(cars); // [Volvo, BMW, Ford, Mazda]
        System.out.println(cars.isEmpty()); // false
        System.out.println(cars.size()); // 4

        cars.remove(0); // removes the element at index 0 (i.e. "Volvo")

        System.out.println();
        System.out.println(cars); // [BMW, Ford, Mazda]
        System.out.println(cars.isEmpty()); // false
        System.out.println(cars.size()); // 3

        cars.remove(1); // removes the element at index 1 (i.e. "Ford")

        System.out.println();
        System.out.println(cars); // [BMW, Mazda]

        cars.add("Mercedes");

        System.out.println();
        System.out.println(cars); // [BMW, Mazda, Mercedes]

        cars.clear();

        System.out.println();
        System.out.println(cars); // []
        System.out.println(cars.isEmpty()); // true
        System.out.println(cars.size()); // 0
  } 
}