Best Java Programs for Beginners and Experienced Programmers

As the adage goes, “practice makes perfect.” This piece of wisdom is true in so many aspects of life, including the world of IT. People who want to become good Java programmers need to practice their skills and become familiar with Java language basics. Experienced Java programmers who wish to upskill need to try out the new programming skills they’ve learned.

This article includes some of the best Java programs for newbies who want to practice Java language basics and more complex programs for expert Java programmers expanding their skillset. We’re here to help Java programmers of all levels!

Contents

Java Program Code Examples

We’ve broken down these Java code examples into Basic and Advanced Java programs. They relate to the above listed Basic and Advanced programs.

Basic Java Program Codes

Hello World:

class HelloWorld

{

public static void main(String args[])

{

System.out.println(“Hello World”);

}

Source

Fahrenheit to Celsius:

import java.util.*;

class FahrenheitToCelsius {

public static void main(String[] args) {

float temperature;

Scanner in = new Scanner(System.in);

System.out.println(“Enter temperature in Fahrenheit”);

temperature = in.nextInt();

temperature = ((temperature – 32)*5)/9;

System.out.println(“temperature in Celsius = ” + temperature);

}

Source

Find Odd or Even:

import java.util.Scanner;

class OddOrEven

{

public static void main(String args[])

{

int x;

System.out.println(“Enter an integer to check if it’s odd or even”);

Scanner in = new Scanner(System.in);

x = in.nextInt();

if (x % 2 == 0)

System.out.println(“The number is even.”);

else

System.out.println(“The number is odd.”);

}

Source

Palindrome:

import java.util.*;

class Palindrome

{

public static void main(String args[])

{

String original, reverse = “”; // Objects of String class

Scanner in = new Scanner(System.in);

System.out.println(“Enter a string to check if it’s a palindrome”);

original = in.nextLine();

int length = original.length();

for (int i = length – 1; i >= 0; i–)

reverse = reverse + original.charAt(i);

if (original.equals(reverse))

System.out.println(“The string is a palindrome.”);

else

System.out.println(“The string isn’t a palindrome.”);

}

Source

Garbage Collection:

import java.util.*;

class GarbageCollection

{

public static void main(String s[]) throws Exception

{

Runtime rs = Runtime.getRuntime();

System.out.println(“Free memory in JVM before Garbage Collection = “+rs.freeMemory());

rs.gc();

System.out.println(“Free memory in JVM after Garbage Collection = “+rs.freeMemory());

}

Source

Display Date and Time:

import java.util.*;

class GetCurrentDateAndTime

{

public static void main(String args[])

{

int day, month, year;

int second, minute, hour;

GregorianCalendar date = new GregorianCalendar();

day = date.get(Calendar.DAY_OF_MONTH);

month = date.get(Calendar.MONTH);

year = date.get(Calendar.YEAR);

second = date.get(Calendar.SECOND);

minute = date.get(Calendar.MINUTE);

hour = date.get(Calendar.HOUR);

System.out.println(“Current date is “+day+”/”+(month+1)+”/”+year);

System.out.println(“Current time is “+hour+” : “+minute+” : “+second);

}

Source

Fibonacci Series:

public class JavaExample {

public static void main(String[] args) {

int count = 7, num1 = 0, num2 = 1;

System.out.print(“Fibonacci Series of “+count+” numbers:”);

for (int i = 1; i <= count; ++i)

{

System.out.print(num1+” “);

/* On each iteration, we are assigning second number

* to the first number and assigning the sum of last two

* numbers to the second number

int sumOfPrevTwo = num1 + num2;

num1 = num2;

num2 = sumOfPrevTwo;

}

Source

Advanced Java Program Codes

Binary Search Algorithm Implementation:

import java.util.Scanner;

class BinarySearch

{

public static void main(String args[])

{

int c, first, last, middle, n, search, array[];

Scanner in = new Scanner(System.in);

System.out.println(“Enter number of elements”);

n = in.nextInt();

array = new int[n];

System.out.println(“Enter ” + n + ” integers”);

for (c = 0; c < n; c++)

array[c] = in.nextInt();

System.out.println(“Enter value to find”);

search = in.nextInt();

first = 0;

last = n – 1;

middle = (first + last)/2;

while( first <= last )

{

if ( array[middle] < search )

first = middle + 1;

else if ( array[middle] == search )

{

System.out.println(search + ” found at location ” + (middle + 1) + “.”);

break;

}

else

last = middle – 1;

middle = (first + last)/2;

}

if (first > last)

System.out.println(search + ” isn’t present in the list.”);

}

Source

Heap Sort:

package org.arpit.java2blog;

import java.util.*;

public class HeapSortMain {

public static void buildheap(int []arr) {

* As last non leaf node will be at (arr.length-1)/2

* so we will start from this location for heapifying the elements

* */

for(int i=(arr.length-1)/2; i>=0; i–){

heapify(arr,i,arr.length-1);

}

public static void heapify(int[] arr, int i,int size) {

int left = 2*i+1;

int right = 2*i+2;

int max;

if(left <= size && arr[left] > arr[i]){

max=left;

} else {

max=i;

}

if(right <= size && arr[right] > arr[max]) {

max=right;

}

// If max is not current node, exchange it with max of left and right child

if(max!=i) {

exchange(arr,i, max);

heapify(arr, max,size);

}

public static void exchange(int[] arr,int i, int j) {

int t = arr[i];

arr[i] = arr[j];

arr[j] = t;

}

public static int[] heapSort(int[] arr) {

buildheap(arr);

int sizeOfHeap=arr.length-1;

for(int i=sizeOfHeap; i>0; i–) {

exchange(arr,0, i);

sizeOfHeap=sizeOfHeap-1;

heapify(arr, 0,sizeOfHeap);

}

return arr;

}

public static void main(String[] args) {

int[] arr={1,10,16,19,3,5};

System.out.println(“Before Heap Sort : “);

System.out.println(Arrays.toString(arr));

arr=heapSort(arr);

System.out.println(“=====================”);

System.out.println(“After Heap Sort : “);

System.out.println(Arrays.toString(arr));

}

Source

Matrix Multiplication:

import java.util.Scanner;

class MatrixMultiplication

{

public static void main(String args[])

{

int m, n, p, q, sum = 0, c, d, k;

Scanner in = new Scanner(System.in);

System.out.println(“Enter the number of rows and columns of first matrix”);

m = in.nextInt();

n = in.nextInt();

int first[][] = new int[m][n];

System.out.println(“Enter elements of first matrix”);

for (c = 0; c < m; c++)

for (d = 0; d < n; d++)

first[c][d] = in.nextInt();

System.out.println(“Enter the number of rows and columns of second matrix”);

p = in.nextInt();

q = in.nextInt();

if (n != p)

System.out.println(“The matrices can’t be multiplied with each other.”);

else

{

int second[][] = new int[p][q];

int multiply[][] = new int[m][q];

System.out.println(“Enter elements of second matrix”);

for (c = 0; c < p; c++)

for (d = 0; d < q; d++)

second[c][d] = in.nextInt();

for (c = 0; c < m; c++) {

for (d = 0; d < q; d++) {

for (k = 0; k < p; k++)

sum = sum + first[c][k]*second[k][d];

multiply[c][d] = sum;

sum = 0;

}

System.out.println(“Product of the matrices:”);

for (c = 0; c < m; c++) {

for (d = 0; d < q; d++)

System.out.print(multiply[c][d]+”\t”);

System.out.print(“”);

}

Source

Remove Elements from an ArrayList:

import java.util.ArrayList;

import java.util.List;

public class RemoveFromListDemo {

public static void main(String[] args) {

List<String> cityList = new ArrayList<String>();

cityList.add(“Delhi”);

cityList.add(“Mumbai”);

cityList.add(“Kolkata”);

cityList.add(“Hyderabad”);

cityList.add(“Bangalore”);

cityList.add(“Mumbai”);

System.out.println(“Original List- ” + cityList);

cityList.remove(1);

cityList.remove(“Mumbai”);

System.out.println(“List after removing elements- ” + cityList);

}

Source

Circular LinkList Program:

public class CreateList {
//Represents the node of list.
public class Node{
int data;
Node next;
public Node(int data) {
this.data = data;
}
}
//Declaring head and tail pointer as null.
public Node head = null;
public Node tail = null;
//This function will add the new node at the end of the list.
public void add(int data){
//Create new node
Node newNode = new Node(data);
//Checks if the list is empty.
if(head == null) {
//If list is empty, both head and tail would point to new node.
head = newNode;
tail = newNode;
newNode.next = head;
}
else {
//tail will point to new node.
tail.next = newNode;
//New node will become new tail.
tail = newNode;
//Since, it is circular linked list tail will point to head.
tail.next = head;
}
}
//Displays all the nodes in the list
public void display() {
Node current = head;
if(head == null) {
System.out.println(“List is empty”);
}
else {
System.out.println(“Nodes of the circular linked list: “);
do{
//Prints each node by incrementing pointer.
System.out.print(” “+ current.data);
current = current.next;
}while(current != head);
System.out.println();
}
}
public static void main(String[] args) {
CreateList cl = new CreateList();
//Adds data to the list
cl.add(1);
cl.add(2);
cl.add(3);
cl.add(4);
//Displays all the nodes present in the list
cl.display();
}
}

Source

SQL Database Connectivity Program:

//STEP 1. Import required packages

import java.sql.*;

public class FirstExample {

// JDBC driver name and database URL

static final String JDBC_DRIVER = “com.mysql.jdbc.Driver”;

static final String DB_URL = “jdbc:mysql://localhost/EMP”;

// Database credentials

static final String USER = “username”;

static final String PASS = “password”;

public static void main(String[] args) {

Connection conn = null;

Statement stmt = null;

try{

//STEP 2: Register JDBC driver

Class.forName(“com.mysql.jdbc.Driver”);

//STEP 3: Open a connection

System.out.println(“Connecting to database…”);

conn = DriverManager.getConnection(DB_URL,USER,PASS);

//STEP 4: Execute a query

System.out.println(“Creating statement…”);

stmt = conn.createStatement();

String sql;

sql = “SELECT id, first, last, age FROM Employees”;

ResultSet rs = stmt.executeQuery(sql);

//STEP 5: Extract data from result set

while(rs.next()){

//Retrieve by column name

int id = rs.getInt(“id”);

int age = rs.getInt(“age”);

String first = rs.getString(“first”);

String last = rs.getString(“last”);

//Display values

System.out.print(“ID: ” + id);

System.out.print(“, Age: ” + age);

System.out.print(“, First: ” + first);

System.out.println(“, Last: ” + last);

}

//STEP 6: Clean-up environment

rs.close();

stmt.close();

conn.close();

}catch(SQLException se){

//Handle errors for JDBC

se.printStackTrace();

}catch(Exception e){

//Handle errors for Class.forName

e.printStackTrace();

}finally{

//finally block used to close resources

try{

if(stmt!=null)

stmt.close();

}catch(SQLException se2){

}// nothing we can do

try{

if(conn!=null)

conn.close();

}catch(SQLException se){

se.printStackTrace();

}//end finally try

}//end try

System.out.println(“Goodbye!”);

}//end main

}//end FirstExample

Source

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