Values and Data Types

Chapter 3

Values and Data Types

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Assignment Questions

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Question 1

Why does Java use the Unicode character set?

Answer

Unicode can represent nearly all languages of the world like English, Hindi, Bengali, Kannada, Arabic, Japanese, etc. Java uses unicode so that applications developed using Java can support a wide range of languages rather than just being limited to English.

Question 2

What are escape sequences in Java? Give three examples.

Answer

An escape sequence is a set of characters that has a special meaning to the Java compiler. In the escape sequence, a character is preceded by a backslash (\). Some examples of escape sequences are \n, \' and \t.

Question 3

What is the result of evaluating the following expression?
(3 + 6 * 7) / 3 + 2

Answer

    (3 + 6 * 7) / 3 + 2
⇒ (3 + 42) / 3 + 2
⇒ 45 / 3 + 2
⇒ 45 / 3 + 2
⇒ 15 + 2
⇒ 17

Question 4

What is a token in Java? Name the tokens available in Java.

Answer

All characters in a Java program are grouped into symbols called Tokens. As you know, a computer program consists of a set of instructions called statements. A statement is composed of various components. Each individual component of a programming statement is referred to as a token. Keywords, Identifiers, Operators, Separators and Literals are five tokens in Java.

Question 5

Why can a keyword not be used as a variable name?

Answer

Keywords are reserved words that have a special meaning to the Java compiler. As Java compiler reserves these words for its own use so they are not available as names for variables or methods.

Question 6

Which of the following are Java keywords?
area, input, class, public, int, x, y, radius, long, Hello java

Answer

class, public, int, long are Java keywords.

Question 7

What are identifiers in Java? List three identifier formation rules.

Answer

Identifiers are used to name different parts of a program such as variables, methods, classes, objects, etc. Three identifier formation rules are:

1. An an identifier can be a sequence of alphabets, digits, underscore and dollar sign characters only.
2. Identifiers cannot start with a digit.
3. An identifier must not be a Keyword or a Boolean or null literal.

Question 8

Explain the following statement — "In Java, total, Total, ToTaL, and TOTAL are all different identifiers."

Answer

Java is a case sensitive language. total, Total, ToTaL, and TOTAL have the same set of letters but they differ in the case of these letters. Therefore, Java considers each of them as a different identifier.

Question 9

Which of the following are invalid identifiers?

i. ten
ii. "Hello"
iii. 5678
iv. Coffee
v. $dollar
vi. 4Variables
vii. _var

Answer

• "Hello" is invalid as identifiers cannot contain double quotes.
• 5678 is invalid as identifiers cannot start with a digit.
• 4Variables is invalid as identifiers cannot start with a digit.

Question 10

How would you print characters like \, ' and " in Java?

Answer

We can print characters like \, ' and " using escape sequences i.e. preceding it with a backslash (\) symbol.

Question 11

Distinguish between the following:

i. Token and Identifier

Answer

ii. Keyword and Identifier

Answer

iii. Character and String Constant

Answer

iv. Integer and float Constant

Answer

Question 12

Distinguish between "A" and 'A'.

Answer

"A" is a string literal of length 1 containing the letter A in uppercase whereas 'A' is a character literal having value of A in uppercase.

Question 13

What is wrong with the following statement?
    float flt = 7895.0345;

Answer

This statement is trying to assign a double literal to a float variable so it will result in a syntax error of incompatible types (possible lossy conversion from double to float). To fix it we need to a f or F at the end of the double literal to make it a float literal as shown below:
    float flt = 7895.0345f;

Question 14

Describe primitive data types in Java.

Answer

Primitive data types are fundamental data types that are an integral part of the Java language and are used to declare a variable.

Question 15

List the size of primitive data types in Java.

Answer

Question 16

Which integer and floating point data types take up the same number of bits in computer memory?

Answer

Both, int and float take up 32 bits in memory. Similarly, both long and double take up 64 bits in memory.

Question 17

What is variable initialisation in Java? What are the default values of the following type of variables? short, int, long, float, double, and char.

Answer

Variable initialisation means assigning value to a variable for the first time. Below are the default values of the different data types:

Question 18

Provide the declaration for two variables called xCoordinate and yCoordinate. Both variables are of type int and both are to be initialised to zero in the declaration.

Answer

int xCoordinate = 0; 
int yCoordinate = 0;

OR

int xCoordinate = 0, yCoordinate = 0; 

Question 19

Write a Java assignment statement that will set the value of the variable interestAmount to the value of the variable balanceAmount multiplied by the value of the variable rate. The variables are of type double.

Answer

double interestAmount = balanceAmount * rate;

Question 20

Explain the statement, "a well-documented code is as important as the correctly working code".

Answer

Writing fully commented code is a good programming style. The primary purpose of comments is to document the code so that even a layman can understand the purpose of the written code. Hence, a well-documented code is as important as the correctly working code.

Question 21

How can you write single line comments in Java?

Answer

Single line comments in Java can be written using //. For example:

// This is an example of single line comment.

Question 22

Write a Java constant declaration that gives the name TAX_RATE to the value 15%.

Answer

final int TAX_RATE = 15;

Question 23

If you want to change the precedence of operations in an expression, which symbols do you use?

Answer

Brackets — () can be used to change operator precedence.

Question 24

What are symbolic constants? How are they useful in writing programs?

Answer

Memory locations whose values cannot be changed within a program are called constants or symbolic constants. The advantages of symbolic constants are:

1. It improves the readability of the program and makes it easier for someone to understand the code.
2. Any unintentional changes to such variables are flagged by the compiler.
3. Later, if there is a change in the value of such variables (e.g. interest rate changed), you just need to modify its value at one place and all the other occurrences will be taken care of automatically.

Question 25

What is the output produced by the following lines of program code?

char x, y;
x = 'y';
System.out.println(x);
y = 'z';
System.out.println(y);
x = y;
System.out.println(x);

Answer

Below is the output produced by this code:

y
z
z

Variable x is assigned a value of character y so the first println prints y. Variable y is assigned a value of character z so the second println prints z. After that variable x is assigned the value of variable y which is the character z so last println prints z.