java array lists code example

Example 1: java arraylist

import java.util.List; //list abstract class
import java.util.ArrayList; //arraylist class

//Object Lists
List l = new ArrayList();
ArrayList a = new ArrayList();

//Specialized List
List<String> l = new ArrayList<String>();
ArrayList<Integer> a = new ArrayList<Integer>();
//only reference data types allowed in brackets <>

//Initial Capacity
List<Double> l = new ArrayList<Double>(5);
//list will start with a capacity of 5
//saves allocation times

Example 2: arraylist in java

import java.util.ArrayList;
public class ArrayListExample
{
   public static void main(String[] args)
   {
      int num = 14;
      // declaring ArrayList with initial size num
      ArrayList<Integer> al = new ArrayList<Integer>(num);
      // append new element at the end of list
      for(int a = 1; a <= num; a++)
      {
         al.add(a);
      }
      System.out.println(al);
      // remove element at index 7
      al.remove(7);
      // print ArrayList after deletion
      System.out.println(al);
      // print elements one by one
      for(int a = 0; a < al.size(); a++)
      {
         System.out.print(al.get(a) + " ");
      }
   }
}

Example 3: arraylist java methds

import java.util.ArrayList;
ArrayList<Integer> myList = new ArrayList<Integer>();
myList.add(0);
myList.remove(0);//Remove at index 0
myList.size();
myList.get(0);//Return element at index 0

Example 4: java arraylist

List<String> expenseTypeList = new ArrayList<>();
        expenseTypeList.add("GENERAL");
        expenseTypeList.add("PURCHASE");
        expenseTypeList.add("PROJECT");