JAVA ARRAYLIST
All in one 10 programs of java arraylist
JAVA ARRAYLIST
The ArrayList class is a resizable array, which can be found in the java.util package.
The difference between a built-in array and an ArrayList in Java, is that the size of an array cannot be modified (if you want to add or remove elements to/from an array, you have to create a new one). While elements can be added and removed from an ArrayList whenever you want. The syntax is also slightly different:
Example
Create an ArrayList object called cars that will store strings:
import java.util.ArrayList; // import the ArrayList class
ArrayList<String> cars = new ArrayList<String>(); // Create an ArrayList object
ADD Items:
Add Items
The ArrayList class has many useful methods. For example, to add elements to the ArrayList, use the add() method:
PROGRAM 1:Add items in arraylist
CODE:
import java.util.ArrayList;
public class Main {
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);
}
}
OUTPUT:
[Volvo, BMW, Ford, Mazda]
PROGRAM 2:
CODE:
import java.util.ArrayList;
public class Main {
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.get(0));
}
}
OUTPUT:
Change an Item
To modify an element, use the set() method and refer to the index number:
PROGRAM 3:change an item name using set keyword
CODE:
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> cars = new ArrayList<String>();
cars.add(“ROHIT”);
cars.add(“Sachin”);
cars.add(“Virat”);
cars.add(“AB”);
cars.add(“Suresh Raina”);
cars.set(0, “MS SHONI”);
System.out.println(cars);
}
}
OUTPUT:
[MS SHONI, Sachin, Virat, AB, Suresh Raina]
Remove an Item
To remove an element, use the remove() method and refer to the index number:
PROGRAM 4:Remove an item suing remove keyword
CODE:
package MyPack;
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> cars = new ArrayList<String>();
cars.add(“ROHIT”);
cars.add(“Sachin”);
cars.add(“Virat”);
cars.add(“AB”);
cars.add(“Suresh Raina”);
cars.set(0, “MS SHONI”);
cars.remove(0);
System.out.println(cars);
}
}
OUTPUT: [Sachin, Virat, AB, Suresh Raina]
To remove all the elements in the ArrayList, use the clear() method:
PROBLEM 5:clear all arraylist by using clear function.
CODE:
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> cars = new ArrayList<String>();
cars.add(“ROHIT”);
cars.add(“Sachin”);
cars.add(“Virat”);
cars.add(“AB”);
cars.add(“Suresh Raina”);
cars.set(0, “MS SHONI”);
cars.clear();
System.out.println(cars);
}
}
OUTPUT:
[]
ArrayList Size
To find out how many elements an ArrayList have, use the size method
PROBLEM 6:check size of a arraylist
CODE:
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> cars = new ArrayList<String>();
cars.add(“ROHIT”);
cars.add(“Sachin”);
cars.add(“Virat”);
cars.add(“AB”);
cars.add(“Suresh Raina”);
cars.set(0, “MS SHONI”);
System.out.println(cars.size());
}
}
OUTPUT:
5
Loop Through an ArrayList
Loop through the elements of an ArrayList with a for loop, and use the size() method to specify how many times the loop should run:
PROBLEM 7:Print arraylist using for loop
CODE:
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> cars = new ArrayList<String>();
cars.add(“RCB”);
cars.add(“CSK”);
cars.add(“MI”);
cars.add(“GT”);
for (int i = 0; i < cars.size(); i++) {
System.out.println(cars.get(i));
}
}
}
OUTPUT:
RCB
CSK
MI
GT
Create an ArrayList to store numbers (add elements of type Integer):
PROBLEM 8:To store integer type of data in arraylist
CODE:
package MyPack;
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<Integer> myNumbers = new ArrayList<Integer>();
myNumbers.add(10);
myNumbers.add(15);
myNumbers.add(20);
myNumbers.add(25);
for (int i : myNumbers) {
System.out.println(i);
}
}
}
OUTPUT:
10
15
20
25
Sort an ArrayList of Integers:
PROBLEM 9: Sort an ArrayList of Integers:
With the help collections packages it will sort suing given command.
CODE:
package MyPack;
import java.util.ArrayList;
import java.util.Collections; // Import the Collections class
public class Main {
public static void main(String[] args) {
ArrayList<Integer> myNumbers = new ArrayList<Integer>();
myNumbers.add(33);
myNumbers.add(15);
myNumbers.add(20);
myNumbers.add(34);
myNumbers.add(8);
myNumbers.add(12);
Collections.sort(myNumbers); // Sort myNumbers
for (int i : myNumbers) {
System.out.println(i);
}
}
}
OUTPUT:
8
12
15
20
33
34
Program 10:Creating 2d arraylist.
CODE:
package MyPack;
import java.util.ArrayList;
public class TwoDimensionalArrayLists{
public static void main(String args[]) {
// Creating 2D ArrayList
ArrayList<ArrayList<Integer> > arrLL = new ArrayList<ArrayList<Integer> >();
// Allocating space to 0th row with the help of ‘new’ keyword
// At 0th row, 0 gets stored in memory by default
arrLL.add(new ArrayList<Integer>());
// At 0th row, modifing the default value to 13
arrLL.get(0).add(0, 13);
System.out.println(“2D ArrayList :”);
// Printing 2D ArrayList
System.out.println(arrLL);
}
}
OUTPUT:
2D ArrayList :
[[13]]
Thank you contributor: Somnath more
Gmail ID:somnathmore0604@gmai.com