Here is a big list of Best Programming questions in java for Job Interviews. As I said, it includes questions from problem-solving, linked list, array, string, matrix, bitwise operators and other miscellaneous parts of programming. Once you are gone through these questions, you can handle a good number of questions on real Job interviews.
You can also try out these programs
Part – 1 for Programming questions in java
//Hello.java
class Hello
{
public static void main(String args[])
{
System.out.println(“Welcome to Java!”);
}
}
Compile: – javac Hello.java
Run Java: – java Hello
Write a program for object and class in java.
class Rectangle
{
privateintl,b;
public void setDimension(intx,int y)
{
l=x;
b=y;
}
publicint area()
{
return l*b;
}
public void display()
{
System.out.println(“Length=”+l);
System.out.println(“Breadth=”+b);
}
public static void main(String ac[])
{
Rectangle r=new Rectangle();
r.setDimension(5,10);
r.display();
System.out.println(“Area=”+r.area());
}
}
Write a program to explain the concept of this keyword in java.
classThisTest
{
int id;
String name;
ThisTest(intid,String name)
{
this.id = id;
this.name = name;
}
void display()
{
System.out.println(id+” “+name);
}
public static void main(String args[])
{
ThisTest s1 = new ThisTest(142,”Shamshad”);
ThisTest s2 = new ThisTest(452,”John”);
s1.display();
s2.display();
}
}
Write a program to explain the concept of super keyword in java.
class Bike
{
int speed=50;
}
class Super extends Bike
{
int speed=100;
void display()
{
System.out.println(super.speed);
}
public static void main(String args[])
{
Super b=new Super();
b.display();
}
}
Write a program for overloading in java.
class Overloading
{
void sum(inta,int b)
{
System.out.println(a+b);
}
void sum(double a,double b)
{
System.out.println(a+b);
}
public static void main(String args[])
{
Overloading obj=new Overloading();
obj.sum(10.5,10.5);
obj.sum(20,20);
}
}
Part – 2 for Programming questions in java
Write an abstract class program in java.
public abstract class shape
{
public abstract void calculatearea();
}
public class circle extends shape
{
privateintx,y;
privateint radius;
public circle()
{
x=15;
y=15;
radius=10;
}
public void calculatearea ()
{
double area=3.14*(radius*radius);
System.out.println(“area=”+area);
}
}
class test1
{
public static void main(String arr[])
{
shape s =null;
s=new circle();
s.calculatearea();
}
}
Write an Interface program in java.
public interface Speaker
{
public void speak();
}
public class Lecturer implements Speaker
{
public void speak()
{
System.out.println(“Lecturer view”);
}
}
public class Politician implements Speaker
{
public void speak()
{
System.out.println(“Politician view”);
}
}
public class Test
{
public static void main(String arr[])
{
Speaker sp=null;
System.out.println(“sp point to politician”);
sp=new Politician();
sp.speak();
System.out.println(“sp point to Lecturer”);
sp=new Lecturer();
sp.speak();
}
}
Write a program for Handling an Exception In java.
classExceptionHandling
{
public static void main(String arr[])
{
try
{
int a=Integer.parseInt(arr[0]);
int b=Integer.parseInt(arr[1]);
int sum = a/b;
System.out.println(“Result:”+ sum);
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Write a program for a Constructor in java.
class A
{
int a;
public A(int x)
{
a=x;
}
public A()
{
System.out.println(“it is default constructor”);
}
{
System.out.println(“it is funny”);
}
public void display()
{
System.out.println(“a=”+a);
}
public static void main(String arg[])
{
A x=new A();
x.display();
A y=new A(10);
y.display();
}
}
to print Fibonacci series in Java
// Dynamic Programming approach for
// Fibonacci Series
class fibonacci {
// Function to find the fibonacci Series
static int fib(int n)
{
// Declare an array to store
// Fibonacci numbers.
// 1 extra to handle case, n = 0
int f[] = new int[n + 2];
int i;
// 0th and 1st number of
// the series are 0 and 1
f[0] = 0;
f[1] = 1;
for (i = 2; i <= n; i++) {
// Add the previous 2 numbers
// in the series and store it
f[i] = f[i – 1] + f[i – 2];
}
// Nth Fibonacci Number
return f[n];
}
public static void
main(String args[])
{
// Given Number N
int N = 10;
// Print first 10 term
for (int i = 0; i < N; i++)
System.out.print(fib(i) + ” “);
}
}
How to convert LinkedList to Array in Java?
// Java program to convert
// LinkedList to Array
import java.util.*;
public class GFG {
// Function to convert LinkedList to Array
public static <T> Object[] convertLinkedListToArray(LinkedList<T> linkedList)
{
// Converting LinkedList to Array
Object[] array = linkedList.toArray();
return array;
}
public static void main(String args[])
{
// Creating linked list
LinkedList<String>
linkedList = new LinkedList<String>();
// Adding elements to the linked list
linkedList.add(“G”);
linkedList.add(“e”);
linkedList.add(“e”);
linkedList.add(“k”);
linkedList.add(“s”);
// Print the LinkedList
System.out.println(“Linked list: “
+ linkedList);
// Converting LinkedList to Object Array
Object[] objArray = convertLinkedListToArray(linkedList);
// Convert Object[] to String[]
String[] array = Arrays.copyOf(objArray,
objArray.length,
String[].class);
// Print the String Array
System.out.println(“Array: “
+ Arrays.toString(array));
}
}
Convert a String to a List of Characters in Java
// Java program to illustrate
// Converting a String to a List
// of Characters
import java.util.*;
// Java program to convert
// a String to a List of Characters
class GFG {
// Function to convert String
// to List of Characters
public static List<Character>
convertStringToCharList(String str)
{
// Create an empty List of character
List<Character> chars = new ArrayList<>();
// For each character in the String
// add it to the List
for (char ch : str.toCharArray()) {
chars.add(ch);
}
// return the List
return chars;
}
// Driver code
public static void main(String[] args)
{
// Get the String to be converted
String str = “Geek”;
// Get the List of Character
List<Character>
chars = convertStringToCharList(str);
// Print the list of characters
System.out.println(chars);
}
}
Part – 3 for Programming questions in java
Final All Permutations of given String Using Recursion and Loop
public class StringPermutations
{
public static void main(String args[])
{
permutation(“123”);
}
/* * A method exposed to client to calculate permutation of String in Java.*/
public static void permutation(String input){
permutation(“”, input);
}
/* * Recursive method which actually prints all permutations
* of given String, but since we are passing an empty String
* as current permutation to start with,
* I have made this method private and didn’t exposed it to client. */ private static void permutation(String perm, String word) {
if (word.isEmpty())
{
System.err.println(perm + word);
}
else
{
for (int i = 0; i < word.length(); i++)
{
permutation(perm + word.charAt(i), word.substring(0, i) + word.substring(i + 1, word.length()));
}
}
}
}
Output: 123 132 213 231 312 321
How to check if two String are Anagram in Java
import java.util.Arrays;
/** * Java program – String Anagram Example.
* This program checks if two Strings are anagrams or not */
public class AnagramCheck {
/* * One way to find if two Strings are anagram in Java. This method
* assumes both arguments are not null and in lowercase.
* * @return true, if both String are anagram */
public static boolean isAnagram(String word, String anagram){
if(word.length() != anagram.length()){
return false;
}
char[] chars = word.toCharArray();
for(char c : chars){
int index = anagram.indexOf(c);
if(index != -1){
anagram = anagram.substring(0,index) + anagram.substring(index +1, anagram.length());
}
else
{
return false;
}
}
return anagram.isEmpty();
}
/* * Another way to check if two Strings are anagram or not in Java * This method assumes that both word and anagram are not null and lowercase
* @return true, if both Strings are anagram. */
public static boolean iAnagram(String word, String anagram){
char[] charFromWord = word.toCharArray();
char[] charFromAnagram = anagram.toCharArray(); Arrays.sort(charFromWord);
Arrays.sort(charFromAnagram);
return Arrays.equals(charFromWord, charFromAnagram);
}
public static boolean checkAnagram(String first, String second){
char[] characters = first.toCharArray();
StringBuilder sbSecond = new StringBuilder(second);
for(char ch : characters){
int index = sbSecond.indexOf(“” + ch);
if(index != -1){
sbSecond.deleteCharAt(index);
}
else
{
return false;
}
}
return sbSecond.length()==0 ? true : false;
}
}
Java Program to Print Spiral Pattern of Numbers
public class GFG {
public static void printSpiral(int size)
{
// Create row and col
// to traverse rows and columns
int row = 0, col = 0;
int boundary = size – 1;
int sizeLeft = size – 1;
int flag = 1;
// Variable to determine the movement
// r = right, l = left, d = down, u = upper
char move = ‘r’;
// Array for matrix
int matrix[][] = new int[size][size];
for (int i = 1; i < size * size + 1; i++) {
// Assign the value
matrix[row][col] = i;
// switch-case to determine the next index
switch (move) {
// If right, go right
case ‘r’:
col += 1;
break;
// if left, go left
case ‘l’:
col -= 1;
break;
// if up, go up
case ‘u’:
row -= 1;
break;
// if down, go down
case ‘d’:
row += 1;
break;
}
// Check if the matrix
// has reached array boundary
if (i == boundary) {
// Add the left size for the next boundary
boundary += sizeLeft;
// If 2 rotations has been made,
// decrease the size left by 1
if (flag != 2) {
flag = 2;
}
else {
flag = 1;
sizeLeft -= 1;
}
// switch-case to rotate the movement
switch (move) {
// if right, rotate to down
case ‘r’:
move = ‘d’;
break;
// if down, rotate to left
case ‘d’:
move = ‘l’;
break;
// if left, rotate to up
case ‘l’:
move = ‘u’;
break;
// if up, rotate to right
case ‘u’:
move = ‘r’;
break;
}
}
}
// Print the matrix
for (row = 0; row < size; row++) {
for (col = 0; col < size; col++) {
int n = matrix[row][col];
System.out.print((n < 10) ? (n + ” “)
: (n + ” “));
}
System.out.println();
}
}
// Driver Code
public static void main(String[] args)
{
// Get the size of size
int size = 5;
// Print the Spiral Pattern
printSpiral(size);
}
}
Output
1 2 3 4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9
