Java Program to demonstrate the use of ArrayList.
Objective
Write a Java program to demonstrate ArrayList operations (add, find, remove).
Algorithm / Approach
- Import
java.util.*. - Instantiate an
ArrayList<Integer>. - Use a loop to continuously ask the user for elements and use
al.add(x)to append them to the list. - Use
al.indexOf(x)to search for an element and return its position. - Use
al.remove(index)to delete an element from the list.
Test.java
import java.util.*;
class Test {
ArrayList<Integer> al;
Scanner s;
Test() {
al = new ArrayList<Integer>();
s = new Scanner(System.in);
}
void addElement() {
char c = 'y';
while(c=='y') {
System.out.print("Enter Element: ");
int x = s.nextInt();
al.add(x);
System.out.print("Want to Add[y/n]: ");
try {
c=(char)System.in.read();
}
catch(Exception e) { }
}
}
void find() {
System.out.print("Element to find: ");
int x = s.nextInt();
int i = al.indexOf(x);
if(i == -1) {
System.out.println("NOT in List");
}
else {
System.out.println("Find at "+(i+1));
}
}
void show() {
System.out.println(al);
System.out.println("Size: "+al.size());
}
void delete() {
System.out.print("Element to delete: ");
int x = s.nextInt();
int index = al.indexOf(x);
if(index == -1) {
System.out.println("NOT in List");
}
else {
al.remove(index);
System.out.println("Now List: "+al);
}
}
public static void main(String[] a)
throws Exception
{
Test t = new Test();
System.out.println("Add in List ");
t.addElement();
t.show();
t.find();
t.delete();
}
}Expected Output
Add in List Enter Element: 1 Want to Add[y/n]: y Enter Element: 2 Want to Add[y/n]: y Enter Element: 3 Want to Add[y/n]: y Enter Element: 4 Want to Add[y/n]: y Enter Element: 5 Want to Add[y/n]: y Enter Element: 6 Want to Add[y/n]: y Enter Element: 7 Want to Add[y/n]: y Enter Element: 8 Want to Add[y/n]: y Enter Element: 9 Want to Add[y/n]: n [1, 2, 3, 4, 5, 6, 7, 8, 9] Size: 9 Element to find: 12 NOT in List Element to delete: 5 Now List: [1, 2, 3, 4, 6, 7, 8, 9]
Explanation of the Program
ArrayListis a part of the Java Collections Framework. It implements theListinterface and provides a dynamic, resizable array.- Unlike standard Java arrays (which have a fixed size upon creation), an ArrayList automatically grows its internal capacity when you add elements, and shrinks when you remove them.
- The
indexOf()method is a convenient built-in Linear Search that returns -1 if the element is not found.
Complexity
Time Complexity
O(n) - For searching and shifting elements during removal.
Space Complexity
O(n)
