Do you possess the necessary skills to ace a Java interview? We are available to assist you with solidifying your Java skills and ideas. Let’s have a brief understanding of Java before we get started.
What is Java?
The high-level programming language Java was created in 1982 by James Gosling. It may be used to create extensive applications and is founded on the ideas of object-oriented programming.
All the frequently asked Java coding interview questions as well as the most popular Core Java, String Handling, Java 8 and multithreading interview questions, Java OOPs, Java exception handling, and collections interview questions are covered in the article that follows.
Java interview question
Java interview question
In this blog post, we present a Java coding quiz with 25+ multiple-choice questions, each accompanied by
detailed
answers and explanations. Let’s get started!
1. What is the output of the following code snippet?
int x = 5;
int y = 10;
System.out.println(x + y + "Hello");
a) 15Hello
b) Hello15
c) 510Hello
d) 5Hello10
Answer:
a) 15Hello
Explanation:
In Java, when the + operator is used with a combination of numbers and strings, it performs
addition
for numbers and concatenation for strings. The expression x + y evaluates to 15, and then “Hello” is
concatenated to it. Therefore, the final output is 15Hello.
2. What is the output of the following code snippet?
The == operator compares the object references. In this case, str1 and str2 refer
to
different objects, even though they contain the same string value. Therefore, the output is
false.
3. What is the output of the following code snippet?
The length property of an array in Java returns the number of elements in the array. In this
case,
the array arr has 5 elements, so the output is 5.
4. What is the output of the following Java program?
publicclassMain{
publicstaticvoidmain(String []args){
int x = 5;
int y = 10;
if (x < y)
System.out.println("x is less than y");
elseif (x > y)
System.out.println("x is greater than y");
else
System.out.println("x is equal to y");
}
}
a) x is less than y
b) x is greater than y
c) x is equal to y
d) The code will not compile due to a syntax error.
Answer:
a) x is less than y
Explanation:
The if condition x < y is true, so the code inside the first if block is executed, resulting
in
the output x is less than y
5. What is the output of the following Java program?
publicclassMain{publicstaticvoidmain(String []args){
int x = 10;
int y = 5;
int z = (x > y) ? x : y;
System.out.println(z);
}
}
a) 10
b) 5
c) 15
d) The code will not compile due to a syntax error.
Answer:
a) 10
Explanation:
The ternary operator (x > y) ? x : y evaluates to x because x is greater than y. Therefore,
the
output is 10.
6. What is the output of the following Java program?
publicclassMain{
publicstaticvoidmain(String []args){
int x = 10;
while (x > 0) {
System.out.print(x + " ");
x--;
}
}
}
a) 10 9 8 7 6 5 4 3 2 1
b) 10 9 8 7 6 5 4 3 2 1 0
c) 1 2 3 4 5 6 7 8 9 10
d) The code will not compile due to a syntax error.
Answer:
a) 10 9 8 7 6 5 4 3 2 1
Explanation:
The while loop iterates as long as the condition x > 0 is true. In each iteration, the value of x is
printed, and then it is decremented. Therefore, the output is “10 9 8 7 6 5 4 3 2 1”.
7. What is the output of the following Java program?
publicclassMain{
publicstaticvoidmain(String []args){
for (int i = 0; i < 5; i++) {
System.out.print(i + " ");
if (i == 2)
break;
}
}
}
a) 0 1 2
b) 0 1 2 3 4
c) 0 1
d) 0 1 2 3 4 5
Answer:
a) 0 1 2
Explanation:
The for loop iterates from 0 to 4. When i becomes 2, the if condition i == 2 is true, and
the
break statement is executed, terminating the loop. Therefore, the output is “0 1 2”.
8. What is the output of the following Java program?
publicclassMain{
publicstaticvoidmain(String []args){
for (int i = 0; i < 5; i++) {
if (i == 2)
continue;
System.out.print(i + " ");
}
}
}
The for loop iterates from 0 to 4. When i becomes 2, the if condition i == 2 is true, and
the
continue statement is executed, skipping the rest of the loop body for that iteration. Therefore, the
output
is “0 1 3 4”.
9. What is the output of the following Java program?
publicclassMain{
publicstaticvoidmain(String []args){
int i = 0;
do {
System.out.print(i + " ");
i++;
} while (i < 5);
}
}
a) 0 1 2 3 4
b) 0 1 2 3 4 5
c) 1 2 3 4 5
d) The code will not compile due to a syntax error.
Answer:
a) 0 1 2 3 4
Explanation:
The do-while loop executes the loop body at least once and continues as long as the condition i < 5
is
true. Therefore, the output is “0 1 2 3 4”.
10. What is the output of the following program?
publicclassMain {publicstaticvoidmain(String[] args){
int x = 10;
int y = x++;
System.out.println(y);
}
}
a) 10
b) 11
c) 9
d) Compile-time error
Answer:
a) 10
Explanation:
The postfix increment operator (x++) first assigns the value of x to y, and then increments the value of
x.
Therefore, the value of y is 10.
11. What will be the output of the following Java program?
Whenever a class gets instantiated, the constructor of its base classes (the constructor of the root of
the
hierarchy gets executed first) gets invoked before the constructor of the instantiated class.
12. What will be the output of the following Java program?
a) The program results in a compiler error (“ambiguous overload”).
b) long
c) Integer
d) int
Answer:
d) int
Explanation:
For an integer literal, the JVM matches in the following order: int, long, Integer, int…. In
other
words, it first looks for an int type parameter; then it looks for long type; and so on.
Here,
since the int type parameter is specified with an overloaded method, it matches with int.
13. What will be the output of the following Java program?
publicclassStrEqual {
publicstaticvoidmain(String[] args) {
String s1 =“hello“;
String s2 =newString(“hello“);
String s3 =“hello“;
if (s1 == s2) {
System.out.println(“s1 and s2 equal“);
} else {
System.out.println(“s1 and s2 not equal“);
}
if (s1 == s3) {
System.out.println(“s1 and s3 equal“);
} else {
System.out.println(“s1 and s3 not equal“);
}
}
}
Which one of the following options provides the output of this program when executed? a)
s1 and s2 equal
s1 and s3 equal
b)
s1 and s2 equal
s1 and s3 not equal
c)
s1 and s2 not equal
s1 and s3 equal
d)
s1 and s2 not equal
s1 and s3 not equal
Answer:
c)
s1 and s2 not equal
s1 and s3 equal
Explanation:
JVM sets a constant pool in which it stores all the string constants used in the type. If two
references
are declared with a constant, then both refer to the same constant object.
The == operator
checks the similarity of the objects themselves (and not the values in it). Here, the first comparison
is
between two distinct objects, so we get s1 and s2 not equal. On the
other
hand, since references to s1 and s3 refer to the same object, we
get s1 and s3 equal.
14. What is the output of the following Java program?
We know that the intern() method will return the String object reference from the
string
pool since we assign it back to s2 and now
both s1 and s2 are having the same reference. It means
that s1 and s2 references point to the same object.
15. What is the output of the following code snippet?
The concat() method returns a new string resulting from concatenating the specified string
to
the original string. However, in this code, the result of concat() is not assigned back to the str variable.
Therefore, the original string “Java” remains unchanged, and the output is “Java”.
16. What is the output of the following code snippet?
The regex pattern “\\d+” is used, which matches one or more digits. Since the input string “1234”
consists of only digits, the regex pattern matches the entire string. Therefore, the output will be
“1234”.
17. What is the output of the following code snippet?
The regex “[a-c]” matches any character between ‘a’ and ‘c’ (inclusive) in a case-sensitive manner. In
the
input string “abcABC”, it matches “a”, “b”, and “c” and prints them.
18. What is the output of the following Java program?
classOne{
publicstaticvoidprint(){
System.out.println("1");
}
}
classTwoextendsOne{
publicstaticvoidprint(){
System.out.println("2");
}
}
publicclassTest{
publicstaticvoidmain(String args[]){
One one = new Two();
one.print();
}
}
a) 2
b) 1
c) Compile-time error
d) Run-time error
Answer:
b) 1
Explanation:
Static methods are defined at the class level. In the case of the static methods, regardless of which
object the reference is pointing to, it always calls the static method defined by the reference class.
Here,
the reference is of type One, so the static method of class One will be called.
19. What is the output of the following Java program?
classOne{
publicvoidprint(){
System.out.println("1");
}
}
classTwoextendsOne{
publicvoidprint(){
System.out.println("2");
}
}
publicclassTest{
publicstaticvoidmain(String args[]){
One one = new Two();
one.print();
}
}
a) 2
b) 1
c) Compile-time error
d) Run-time error
Answer:
a) 2
Explanation:
Even though the reference type of object one is One, the actual object it points to is of type
Two due to polymorphism. When we call the print method on One, the JVM dynamically binds
the
call to the print method in class Two at runtime. As a result, “2” is printed on the console.
20. What is the output of the following Java program?
classOne{
publicOne(int x){
System.out.print("int constructor");
}
publicOne(long l){
System.out.print("long constructor");
}
}
publicclassTest{
publicstaticvoidmain(String[] args){
long l = 20L;
One one = new One(l);
}
}
a) int constructor
b) long constructor
c) Compile-time error
d) Run-time error
Answer:
b) long constructor
Explanation:
When we create object one with the long variable l as an argument, the constructor with
the
long parameter in class One is called. As a result, the “long constructor” is printed to the
console.
If you pass an int parameter in class One then it will print “int constructor” to the
console.
21. What is the output of the following Java program?
When overriding a parent class method in a child class, we cannot reduce the visibility of the method.
For
example, if the method is defined as public in the parent class, a child class cannot override it with
protected. The code will give the compilation error “Cannot reduce the visibility of the inherited
method
from Parent”.
22. What is the output of the following Java program?
classDemo{
publicDemo(int i){
System.out.println("int");
}
publicvoidDemo(short s){
System.out.println("short");
}
}
publicclassTest{
publicstaticvoidmain(String[] args){
short s = 10;
Demo demo = new Demo(s);
}
}
a) int
b) short
c) Compile-time error
d) Run-time error
Answer:
a) int
Explanation:
The class Demo has one constructor i.e. with int argument. The short value is
automatically promoted to an int value during object creation so the constructor with the
int
argument will be called and it will print “int”.
23. What is the output of the following Java program?
Java constructors do not have a return type. If you mention the return type, it automatically becomes a
method instead of a constructor. Hence, the void Demo() becomes a method of the class Demo
and
thus it will not be called when an object of the class Demo is created.
24. What is the output of the following Java program?
classOne{
publicOne(){
System.out.print("One,");
}
}
classTwoextendsOne{
publicTwo(){
System.out.print("Two,");
}
}
classThreeextendsTwo{
publicThree(){
System.out.print("Three");
}
}
publicclassTest{
publicstaticvoidmain(String[] args){
Three three = new Three();
}
}
a) Three
b) One
c) One,Two,Three
d) Run-time error
Answer:
c) One,Two,Three
Explanation:
When we create an object of class Three, the constructors are executed in the following
order:
One(): Prints “One,”.
Two(): Prints “Two,”.
Three(): Prints “Three”.
So, the overall output is “One,Two,Three”. The constructors are executed in the order of inheritance
hierarchy from the topmost superclass (One) to the subclass (Three).
25. What is the output of the following Java program?
The execution of the Java program starts from the main() method so it will print “Hello World!”
26. What is the output of the following Java program?
publicclassMain{
staticString name = "Ramesh";
publicMain(){
name = "Prabhas";
}
publicstaticvoidmain(String[] args){
System.out.println("The name is " + name);
}
}
a) Prabhas
b) The name is Ramesh
c) No Output
d) Run-time error
Answer:
b) The name is Ramesh
Explanation:
The name String variable is declared as static and initialized with the string “Ramesh”. The
value
of the name variable is changed in the constructor. However, the class constructor is called only
when an object is created. The code does not create any objects of the class Test, and hence the
constructor
is never called. So the value of the name variable remains unchanged.
27. What will be the output of the following program?
classFirst{
staticvoidstaticMethod()
{
System.out.println("Static Method");
}
}
publicclassMainClass{
publicstaticvoidmain(String[] args)
{
First first = null;
first.staticMethod();
}
}
a) Static Method
b) Throws a NullPointerException
c) Compile-time error
d) Runtime error
Answer:
a) Static Method
Explanation:
The provided Java code will compile and execute successfully without any exceptions. When calling a
static
method, it doesn’t require an instance of the class. Therefore, you can call the static method
staticMethod() from class First using the null reference first.
Post Comment