Java interview questions

Java Interview Questions:

1. Method overloading:

public class MethodReference {
public void saySomething(){
System.out.println("Hello, this is static method.");
}

public static void apply(Integer i) {
System.err.println("Integer-" + i);
}
public static void apply(String k) {
System.err.println("String-"+k);
}
public static void main(String[] args) {

MethodReference.apply(null);

for(int i =1;i<=3;i++) {
for(int j =1;j<=i;j++) {
System.out.print("* ");
}
System.out.println();
}
}

}

public class MethodReference {

public void saySomething(){

System.out.println("Hello, this is static method.");

}

public static void apply(Integer i) {

System.err.println("Integer-" + i);

}

public static void apply(String k) {

System.err.println("String-"+k);

}

public static void main(String[] args) {

MethodReference.apply(null);

for(int i =1;i<=3;i++) {

for(int j =1;j<=i;j++) {

System.out.print("* ");

}

System.out.println();

}

Options:

a. Compile time exception

b. Run rime exeption

c. String-null

d. Integer-null

Ans: a

2. How to find sum of an array?

Sol:

package com;

public class ArraySum {

// declare and initialize a variable named sum
static int sum = 0;

public static void main(String[] args) {

// declaring array variable and assigning
int a[] = {10,20,30,40,50};

for(int i=0; i<a.length; i++){ // Here length of an array is 5

sum = sum + a[i]; // script executes 5 times to find the sum

}

// print the result
System.out.println("Sum of an array is: "+sum);
System.out.println("Lenght of an array is: "+a.length);
}

}

package com;

public class ArraySum {

// declare and initialize a variable named sum

static int sum = 0;

public static void main(String[] args) {

// declaring array variable and assigning

int a[] = {10,20,30,40,50};

for(int i=0; i<a.length; i++){ // Here length of an array is 5

sum = sum + a[i]; // script executes 5 times to find the sum

}

// print the result

System.out.println("Sum of an array is: "+sum);

System.out.println("Lenght of an array is: "+a.length);

}

Output:

Sum of an array is: 150
Lenght of an array is: 5

3: Which of the following access specifier makes a declaration that is accessible to itself?

a. public

b. private

c. protected

d. privately

Ans: b

4: Which of the following statement is true with respect to class and members of a class?

a. It is mandatory for every class to declare a main method inside it.

b. It is mandatory to specify return type along with method definition in a class.

c. It is mandatory to initiate member variables while declaring them in a class.

d. It is mandatory to use an access specifier along with declaring statement of a member variable.

Ans: Will reveal soon.

5: What is the output of below code?

public void array(){

String[] arr = new String[4];
arr[0] = "zero";
arr[1] = "one";

for(int i=0;i<arr.length;i++){
System.out.println("output is: "+arr[i]);
}
}

public void array(){

String[] arr = new String[4];

arr[0] = "zero";

arr[1] = "one";

for(int i=0;i<arr.length;i++){

System.out.println("output is: "+arr[i]);

}

a. output is: zero
output is: one

b. Runtime error

c. output is: zero
output is: one
output is: null
output is: null

d. Compilation error

Ans: C

6: What is the output of below code?

// 
public void arrayList(){

ArrayList<String> arrayList = new ArrayList<String>();

arrayList.add("zero");
arrayList.add("one");

for(int i=0;i<arrayList.size();i++){
System.out.println("output is: "+arrayList.get(i));
}
}

public void arrayList(){

ArrayList<String> arrayList = new ArrayList<String>();

arrayList.add("zero");

arrayList.add("one");

for(int i=0;i<arrayList.size();i++){

System.out.println("output is: "+arrayList.get(i));

}

Options:

a. output is: zero
output is: one
b. Compilation error
c. Runtime error
d. ArrayIndexOutOfBounds Exception

Ans: a

7. Write a code to find the sum of numbers between two given positions in an array.

Ans:

// Sum of numbers between two given indexes in an array
public void arrayRandomCount2(){
// find the sum of numbers between 5th and 15th index position.
int n1;
int n2;
int a=0,b=0;
boolean b1=true;
int i=0,sum=0;

int[] arr = { 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100};
System.out.println("Array length is: "+arr.length);

n1=25;
n2=75;

for(i=0;i<arr.length;i++){
if(n1==(arr[i]) || n2==arr[i] ){
System.out.println("n1 position is: "+i);
if(b1==true)
{
a=i;
b1=false;
}
else
b=i;
}
}

for(i=a+1;i<b;i++){
    sum = sum + arr[i];
}

System.out.println("Total sum is: "+sum);
}

// Sum of numbers between two given indexes in an array

public void arrayRandomCount2(){

// find the sum of numbers between 5th and 15th index position.

int n1;

int n2;

int a=0,b=0;

boolean b1=true;

int i=0,sum=0;

int[] arr = { 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100};

System.out.println("Array length is: "+arr.length);

n1=25;

n2=75;

for(i=0;i<arr.length;i++){

if(n1==(arr[i]) || n2==arr[i] ){

System.out.println("n1 position is: "+i);

if(b1==true)

{

a=i;

b1=false;

}

else

b=i;

}

for(i=a+1;i<b;i++){

sum = sum + arr[i];

}

System.out.println("Total sum is: "+sum);

}

Ans:

Array length is: 20
n1 position is: 4
n1 position is: 14
Total sum is: 450

8. Write a code to find out first max number and then first minimum number and so on in a sorted/unsorted array?

Sol:

// Array - Maximum - Minimum - Sort
public void sortArray(){
int[] arr = {2,1,4,3,5,6,12,7,9,8,10,11};
int i, arrayLength;
Arrays.sort(arr);
arrayLength = arr.length;
System.out.println("Array length is: "+arr.length);

for(i=0; i<arrayLength/2; i++){
int j = arrayLength-(i+1);

System.out.print(arr[j]+" ");
System.out.print(arr[i]+" ");

}
if (arrayLength % 2 != 0)
System.out.print(arr[i]);

}

// Array - Maximum - Minimum - Sort

public void sortArray(){

int[] arr = {2,1,4,3,5,6,12,7,9,8,10,11};

int i, arrayLength;

Arrays.sort(arr);

arrayLength = arr.length;

System.out.println("Array length is: "+arr.length);

for(i=0; i<arrayLength/2; i++){

int j = arrayLength-(i+1);

System.out.print(arr[j]+" ");

System.out.print(arr[i]+" ");

}

if (arrayLength % 2 != 0)

System.out.print(arr[i]);

}

9. What is the output for below code snippet?

public class JavaQuestions {
static int j = 20;

public static void main(String argv[]) {
int i = 10;
JavaQuestions java = new JavaQuestions();
java.method1(i);
System.out.print(i+" ");
System.out.println(j);
}

public void method1(int x) {
x = x * 2;
j = j * 2;
}
}

public class JavaQuestions {

static int j = 20;

public static void main(String argv[]) {

int i = 10;

JavaQuestions java = new JavaQuestions();

java.method1(i);

System.out.print(i+" ");

System.out.println(j);

}

public void method1(int x) {

x = x * 2;

j = j * 2;

}

Options:

a. 10 20
b. 20 40
c. 10 40
d. 20 80

Ans: c

10. What is the output of below code snippet? String manipulations.

public class Number {
public static void main(String argv[]) {
boolean b1 = true;
if ((b1 == true) || area(true)) {
System.out.println("Selenium99");
}
}

public static boolean area(boolean place) {
if (place == true) {
System.out.println("First");
}
System.out.println("Second");
return true;
}
}

public class Number {

public static void main(String argv[]) {

boolean b1 = true;

if ((b1 == true) || area(true)) {

System.out.println("Selenium99");

}

public static boolean area(boolean place) {

if (place == true) {

System.out.println("First");

}

System.out.println("Second");

return true;

}

Options:

a. First Second
b. Selenium99
c. First Second Selenium99
d. Selenium99 First Second

Ans:

10.1. Find the output. String manipulations.

// String manipulations

String str1 = new String("selenium99");
String str2 = new String("SELENIUM99");
System.out.println(str1 = str2);

// String manipulations

String str1 = new String("selenium99");

String str2 = new String("SELENIUM99");

System.out.println(str1 = str2);

Options:

a. false

b. true

c. SELENIUM99

d. selenium99

Ans: c

Tags: Java interview questions

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