Syntax Questions
- Give the syntax of the if statement with an example.
Syntax:if(<condition>){ <statement(s)> }
Example:
if(marks >= 40) System.out.println("Pass");
- Write the syntax/general format of for statement. Give an example.
Syntax:for(<initialization>; <boolean expression>; <increment/decrement>){ <statement(s)> }
Example:
for(i = 1; i <= 10; i++) System.out.println(i);
Counters and Accumulators
- Given the three Java statements, state which one among them is a counter and which one an accumulator:
a.i++;
(counter)
b.a = a + 5;
(accumulator)
c.a += 5;
(accumulator)
Output-based Questions
- Write the output of the following code in Java:
int a = 8, b = 18;
System.out.println("a = " + a + "\tb = " + b);
System.out.println("Sum + " + (a + b));
System.out.println("Difference = " + (b - a));
OUTPUT:a = 8 b = 18 Sum + 26 Difference = 10
- Find the output:
int x = 4, y = 81;
System.out.println(x > y);
System.out.println(Math.sqrt(y));
System.out.println(++x + (y % x));
OUTPUT:false
9.0
6 - If a = 24 and b = 12, then find and display the values of a, b, and c in the following expression:
c = a++ - --b;
a = 25.
b = 11.
c = 24 – 11 = 13. - Find the output of the given code:
int a = 5, b = 2, c = 8;
b += ++a - b;
c -= a++ + ++b;
System.out.print("a = " + a + "\nb = " + b + "\nc = " + c);
b = b + ++a – b
⇒b = 2 + 6 – 2 = 6
c = c – (a++ + ++b)
⇒c = 8 – (6 + 7) = -5
OUTPUT:
a = 7
b = 7
c = -5 - Find the output for the following code:
int a = 5, b = 3;
b += ++a + a++;
System.out.print("a = " + a + "\nb = " + b);
OUTPUT:a = 7
b = 15
Theory Questions:
- Differentiate between if and if-else with example.
The if statement contains statements only for the true block.if(marks >= 40) System.out.println("Pass");
The if-else statement contains statements both for true and false block.
if(marks>= 40) System.out.println("Pass"); else System.out.println("Fail");
- What are Java Tokens? Name three of them.
Java tokens are the basic building blocks of a Java program.
Keywords, Identifiers and Literals are three Java tokens. - What is Java? When was it invented and by whom?
Java is an object-oriented, platform-independent programming language.
It was developed in 1991 by James Gosling, but the first version was released in the year 1995. - Why is Java called a platform independent language?
When a Java program is compiled, it produces bytecode, which is platform independent because it can execute in any platform, having JVM. Thus, Java is called a platform independent language. - What is the difference between variable and keyword?
Variables are also known as identifiers in Java. They are the named storage locations that hold values.
Example:int x = 5; //x is a variable
Keywords are special words in Java that have a special meaning to the compiler.
Example:public
,static
,void
. - Differentiate between = and == in Java.
The = sign is an assignment operator. It is used to assign a value to a variable.
Example:int x = 5;
The == sign is a relational operator. It is used to compare two values for equality.
Example:if(x == y) System.out.println("Same");
- State the difference between
System.out.print()
andSystem.out.println()
with an example for each.
The print() method displays the message and keeps the cursor on the same line.
Example:System.out.print("Hello ");
System.out.print("World");
OUTPUT:Hello World
The println() method displays the message and takes the cursor to the next line.
Example:System.out.println("Hello ");
System.out.println("World");
OUTPUT:Hello
World - Differentiate between prefix and postfix.
In prefix, the variable first updates its value, and then assigns it.
Example:int x = 5;
int y = ++x; //y gets 6
Whereas in postfix, the variable first assigns its value, then later it updates it.
Example:int x = 5;
int y = x++; //y gets 5 - Differentiate between a counter and an accumulator.
A counter is a variable that increments/decrements its value by 1 each time. They are mainly used to count a certain operation that repeats in a program.
Example:x++;
An accumulator is a variable that updates its value, but not by 1. They are mainly used to find the result of a calculation that involves many values, like the total sum, factorial, etc.
Example:x += 5;
- State the function of
Math.pow()
andMath.sqrt()
, with an example each.Math.pow()
function returns the value of the first argument raised to the power of the second argument.
Example:double p = Math.pow(2, 3); //p gets 8.0
Math.sqrt()
function returns the square root of a positive number.
Example:double s = Math.sqrt(49); //s gets 7.0
- State any three rules for naming a variable in Java.
Following are the three rules for naming variables in Java:
a. Variable names can begin with a letter, underscore or dollar sign.
b. Variables can’t be the same as the keywords.
c. Variables are case-sensitive. - Write the symbols and names of the logical operators. What is their order of precedence?
The three logical operators are Logical AND (&&), Logical OR (||) and Logical NOT (!). The order of precedence is NOT –> AND –> OR.
Conditional Operators
- Rewrite without using if:
if(bill < 7000) discount = 0.05; else discount = 0.1;
discount = (bill < 7000)? 0.05 : 0.1;
- Give the syntax of the ternary operator and also an example.
Syntax:<variable> = (<boolean expression>)? <value 1> : <value 2>;
Example:int max = (a > b)? a : b;
- Rewrite the given code without using ternary operator:
double ans = (value > 10000)? 0.05 * value : 0.02 * value;
double ans; if(value > 10000) ans = 0.05 * value; else ans = 0.02 * value;
Debug the Errors
- Find and correct the errors (if any):
Circle class { public static voidmain(string args[]) { double a = 75.57d, 12.56d, 11.73d, smo = 0.0d a + b + c = sum; System.out.println("Sum of numbers = " + sum); } }
Correct Code:
class Circle { public static void main(String args[]) { double a = 75.57d, b = 12.56d, c = 11.73d, sum = 0.0d; sum = a + b + c; System.out.println("Sum of numbers = " + sum); } }
Java Expressions:
- Write the following expression in one Java statement:
t = 3 / 7 (a7 + d4)t = 3.0 / 7 * (Math.pow(a, 7) + Math.pow(d, 4));
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