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Chapter 1 - Unit 4

Operators in Java

Class 10 - APC Understanding Computer Applications with BlueJ


State whether the following statements are 'True' or 'False'

Question 1

The precedence of operators in Java follows BODMAS.
False

Question 2

The output of a++ will be 1, if int a = -1.
False

Question 3

The relational operators always result in terms of 'True' or 'False'.
True

Question 4

Given: int m=5; m*=5 then the value stored in m results in 55.
False

Question 5

The statement (a>b)&&(a>c) uses a logical operator.
True

Question 6

If int a=27,b=4,c=0; then c = a%b; results in 3.
True

Question 7

The statement p+=5 means p=p*5.
False

Question 8

In the precedence of logical operators; NOT is followed by AND.
True

Write the Java expressions for the following

Question 1

z = 5x3 + 2yx + y

Answer

z = 5 * x * x * x + 2 * y * x + y

Question 2

m = a2 + b2 / (a + b)

Answer

m = (a * a + b * b) / (a + b)

Question 3

s = ut + (1/2)at2

Answer

s = u * t + (1.0 / 2) * a * t * t

Question 4

f = uv / (u + v)

Answer

f = u * v / (u + v)

Question 5

d = √(3x + x2) / a + b

Answer

d = Math.sqrt(3 * x + x * x) / (a + b)

Question 6

p = a2 + b2 + 2ab

Answer

p = a * a + b * b + 2 * a * b

Question 7

y = 2(lb + bh + lh)

Answer

y = 2 * (l * b + b * h + l * h)

Question 8

p = a / b2 + b / a2

Answer

p = a / (b * b) + b / (a * a)

Question 9

z = x3 + y3 - y / z3

Answer

z = x * x * x + y * y * y - y / (z * z * z)

Question 10

q = 1 / √(a + b) + 3 / c2

Answer

q = (1 / Math.sqrt(a + b)) + 3 / (c * c)

Predict the output

Question 1

int c = (3<4)? 3*4:3+4;

Output
12
Explanation

As 3 is less than 4 so condition of ternary operator is true. Variable c is assigned the value of expression 1 which is 3 * 4 = 12.

Question 2

int a = 14, b = 4;
boolean x = (a > b) ? true : false;

Output
true
Explanation

As 14 is greater than 4 so condition of ternary operator is true. Variable x is assigned the value of expression 1 which is true.

Question 3

int x = 90;
char c = (x<=90)?'Z':'I';

Output
Z
Explanation

As value of x is 90 so condition of ternary operator is true. Variable c is assigned the value of expression 1 which is Z.

Question 4

int a = 18; int b = 12;
boolean t = (a > 20 && b < 15)? true : false;

Output
false
Explanation

The condition a > 20 is false as value of a is 18. So the logical AND operator — && returns false. Variable t is assigned the value of expression 2 which is false.

Question 5

c = (val + 550 < 1700)? 200: 400;
if: (a) val = 1000         (b) val = 1500

Output
(a) 200
(b) 400
Explanation

When val = 1000, val + 550 = 1550. As 1550 is less than 1700 so condition of ternary operator is true. Variable c is assigned the value of expression 1 which is 200.
When val = 1500, val + 550 = 2050. As 2050 is greater than 1700 so condition of ternary operator is false. Variable c is assigned the value of expression 2 which is 400.

Answer the following questions

Question 1

What is an operator? What are the three main types of operators? Name them.

Answer

An operator is a symbol or sign used to specify an operation to be performed in Java programming. The three main types of operators are Arithmetical, Logical and Relational.

Question 2

How is Java expression different from statement?

Answer

An expression is a set of variables, constants and operators i.e. an expression is a combination of operators and operands. When an expression is assigned to a variable, the complete set is referred to as a statement.

Question 3

Explain the following with one example each.

(a) Arithmetic operator

Answer

Arithmetic operators are used to perform mathematical operations on its operands. Operands of arithmetic operators must be of numeric type. A few arithmetic operators operate upon one operand. They are called Unary Arithmetic operators. Other arithmetic operators operate upon two operands. They are called Binary Arithmetic operators. As an example consider the below statement:
int a = 10 + 20;
Here, the addition arithmetic operator, represented by the symbol + will add 10 and 20. So variable a will be 30.

(b) Relational operator

Answer

Relational operators are used to determine the relationship between the operands. Relational operators compare their operands to check if the operands are equal to ( == ), not equal to ( != ), less than ( < ), less than equal to ( <= ), greater than ( > ), greater than equal to ( >= ) each other. The result of an operation involving relation operators is a boolean value — true or false.
Example:
int a = 8;
int b = 10;
boolean c = a < b;
Here, as a is less than b so the result of a < b is true. Hence, boolean variable c becomes true.

(c) Logical operator

Answer

Logical operators operate on boolean expressions to combine the results of these boolean expression into a single boolean value.
Example:
int a = 7;
int b = 10;
boolean c = a < b && a % 2 == 0;
Here, the result of first boolean expression a < b is true and the result of second boolean expression a % 2 is false. The logical AND operator ( && ) combines these true and false boolean values and gives a resultant boolean value as false. So, boolean variable c becomes false.

(d) Ternary operator

Answer

Ternary operator operates on three operands. Its syntax is:
condition ? expression 1 : expression 2
Ternary operator evaluates the condition. If the condition is true then result of ternary operator is the value of expression 1. Otherwise the result is the value of expression 2.
Example:
boolean isLeapYear = true;
int febDays = isLeapYear ? 29 : 28;
Here, the ternary operator checks if the value of boolean variable isLeapYear is true or false. As it is true, expression 1, which in this example is the value 29, is the result of the ternary operator. So, int variable febDays becomes 29.

Question 4

Distinguish between:

(a) Unary & Binary arithmetic operator

Answer

Unary Arithmetic OperatorBinary Arithmetic Operator
It operates on a single operandIt operates on two operands
Increment (++) and Decrement (--) operators are examples of Unary Arithmetic OperatorsMultiplication (*) and Division (/) are examples of Binary Arithmetic Operators

(b) Postfix increment and Prefix increment

Answer

Postfix IncrementPrefix Increment
It works on the principle of USE-THEN-CHANGE.It works on the principle of CHANGE-THEN-USE.
The increment operator (++) is written after the operand.The increment operator (++) is written before the operand.
Example:
int a = 99;
int b = a++;
After the execution of these two statements, a will have the value of 100 and b will have the value of 99.
Example:
int a = 99;
int b = ++a;
After the execution of these two statements, both a and b will have the value of 100.

(c) Postfix decrement and Prefix decrement

Answer

Postfix DecrementPrefix Decrement
It works on the principle of USE-THEN-CHANGE.It works on the principle of CHANGE-THEN-USE.
The decrement operator (--) is written after the operand.The decrement operator (--) is written before the operand.
Example:
int a = 100;
int b = a--;
After the execution of these two statements, a will have the value of 99 and b will have the value of 100.
Example:
int a = 100;
int b = --a;
After the execution of these two statements, both a and b will have the value of 99.

(d) (p != q) and !(p == q)

Answer

(p != q)!(p == q)
This expression uses the relational operator != (Not equal to) to determine if values of p and q are different.This expression first checks if values of p and q are equal using the relation operator == (equality). It then inverts the result of equality operator using the logical NOT (!) operator to determine if values of p and q are different.

Question 5

What is the difference between

(a) / and % operator?

Answer

Division operatorModulus operator
Returns the quotient of division operationReturns the remainder of division operation
Example: int a = 5 / 2; Here a will get the value of 2 which is the quotient of this division operationExample: int b = 5 % 2; Here b will get the value of 1 which is the remainder of this division operation

(b) = and == ?

Answer

===
It is the assignment operator used for assigning a value to a variable.It is the equality operator used to check if a variable is equal to another variable or literal.
Example:
int a = 10;
This statement assigns 10 to variable a.
Example:
if (a == 10)
This statement checks if variable a is equal to 10 or not.

Question 6(a)

What will be the output of the following code?

int k=5,j=9;
k+= k++ - ++j + k;
System.out.println("k="+k);
System.out.println("j="+j);
Output
k=6
j=10
Explanation

    k+= k++ - ++j + k
k = k + (k++ - ++j + k)
k = 5 + (5 - 10 + 6)
k = 5 + 1
k = 6

Question 6(b)

If int y =10 then find int z = (++y*(y+++5));

Output
z = 176
Explanation

    z = (++y*(y+++5))
z = (11 * (11 + 5))
z = (11 * 16)
z = 176

Question 6(c)

Give the output of the following expression:
a+= a++ + ++a + --a + a--; when a = 7;

Output
a = 39
Explanation

    a+= a++ + ++a + --a + a--
a = a + (a++ + ++a + --a + a--)
a = 7 + (7 + 9 + 8 + 8)
a = 7 + 32
a = 39

Question 6(d)

What is the value of y after the execution?
y+= ++y + y-- + --y; when int y=8

Output
y = 33
Explanation

    y+= ++y + y-- + --y
⇒ y = y + (++y + y-- + --y)
⇒ y = 8 + (9 + 9 + 7)
⇒ y = 8 + 25
⇒ y = 33

Question 7

Rewrite the following program segment using if-else statements instead of the ternary operator.

(a) String grade = (marks>=90)?"A": (marks>=80)? "B": "C";

Answer

String grade;
if (marks >= 90)
    grade = "A";
else if (marks >= 80)
    grade = "B";
else
    grade = "C";

(b) commission = (sale > 5000) ? sale*10/100 : 0;

Answer

if (sale > 5000)
    commission = sale * 10 / 100;
else
    commission = 0;

(c) net = (salary > 10000) ? salary - (8.33/100)*salary : salary - (5/100)*salary

Answer

if (salary > 10000)
    net = salary - (8.33/100) * salary;
else
    net = salary - (5/100) * salary;

(d) s = (a + b < c || a + c <= b || b + c <= a) ? "Triangle is not possible": "Triangle is possible";

Answer

if (a + b < c || a + c <= b || b + c <= a)
    s = "Triangle is not possible";
else
    s = "Triangle is possible";

(e) c = (x >= 'A' && x<= 'Z') ? "Upper Case Letter" : "Lower Case Letter";

Answer

if (x >= 'A' && x <= 'Z')
    c = "Upper Case Letter";
else
    c = "Lower Case Letter";

Question 8

Rewrite the following using ternary operator.

(a)

if (x % 2 == 0)
    System.out.println("Even");
else
    System.out.println("Odd");

Answer

System.out.println(x % 2 == 0 ? "Even" : "Odd");

(b)

if (bill > 10000)
    discount=bill*10.0/100;
else
    discount=bill*5.0/100;

Answer

discount = bill > 10000 ? bill*10.0/100 : bill*5.0/100;

(c)

if(income < 10000)
    tax = 0;
else
    tax = 12;

Answer

tax = income < 10000 ? 0 : 12;

(d)

if(a > b)
{
    if (a > c)
        g = a;
    else
        g = c;
}
else if (b > c)
    g = b;
else
    g = c;

Answer

g = a > b ? a > c ? a : c : b > c ? b : c;

(e)

if (p >= 4750)
    k = p * 5 / 100;
else
    k = p * 10 / 100;

Answer

k = (p >= 4750) ? p * 5 / 100 : p * 10 / 100;
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