Question 1

Question 1Why does Java use the Unicode character set?

Accepted 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

Question 2What are escape sequences in Java? Give three examples.

Accepted 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 
, \' and 	.

Question 3

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

Accepted Answer

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

Question 4

Question 4What is a token in Java? Name the tokens available in Java.

Accepted 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

Question 5Why can a keyword not be used as a variable name?

Accepted 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

Question 6Which of the following are Java keywords?area, input, class, public, int, x, y, radius, long, Hello java

Accepted Answer

class, public, int, long are Java keywords.

Question 7

Question 7What are identifiers in Java? List three identifier formation rules.

Accepted Answer

Identifiers are used to name different parts of a program such as variables, methods, classes, objects, etc. Three identifier formation rules are:An an identifier can be a sequence of alphabets, digits, underscore and dollar sign characters only.Identifiers cannot start with a digit.An identifier must not be a Keyword or a Boolean or null literal.

Question 8

Question 8Explain the following statement — "In Java, total, Total, ToTaL, and TOTAL are all different identifiers."

Accepted 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

Question 9Which of the following are invalid identifiers?i. tenii. "Hello"iii. 5678iv. Coffeev. $dollarvi. 4Variablesvii. _var

Accepted 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

Question 10How would you print characters like \, ' and " in Java?

Accepted Answer

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

Question 11

Question 11Distinguish between the following:i. Token and Identifier

Accepted Answer

TokenIdentifierEach individual component of a programming statement is referred to as a token.Identifiers are fundamental building blocks of the program and are used to name different components of a program such as variables, methods and objects.Tokens in Java are categorised into 5 types — Keywords, Identifiers, Literals, Punctuators, Operators.Identifier is a type of token in Java.ii. Keyword and IdentifierKeywordIdentifierKeywords have a special meaning for Java compiler.Identifiers are used to name different components of a program such as variables, methods and objects.Keywords are reserved by the compiler for its own use.An identifier must not be a Keyword.iii. Character and String ConstantCharacter ConstantString ConstantCharacter Constants are written by enclosing a character within a pair of single quotes.String Constants are written by enclosing a set of characters within a pair of double quotes.Character Constants are assigned to variables of type char.String Constants are assigned to variables of type String.iv. Integer and float ConstantInteger ConstantFloat ConstantInteger Constants represent whole number values like 2, -16, 18246, 24041973, etc.Float Constants represent fractional numbers like 3.14159, -14.08, 42.0, 675.238, etc.Integer Constants are assigned to variables of data type — byte, short, int, long, charFloat Constants are assigned to variables of data type — float, double

Question 12

Question 12Distinguish between "A" and 'A'.

Accepted 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

Question 13What is wrong with the following statement?    float flt = 7895.0345;

Accepted 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

Question 14Describe primitive data types in Java.

Accepted 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

Question 15List the size of primitive data types in Java.

Accepted Answer

Data TypeSize in Bytesbyte1short2int4long8float4double8char2boolean1

Question 16

Question 16Which integer and floating point data types take up the same number of bits in computer memory?

Accepted Answer

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

Question 17

Question 17What is variable initialisation in Java? What are the default values of the following type of variables? short, int, long, float, double, and char.

Accepted Answer

Variable initialisation means assigning value to a variable for the first time. Below are the default values of the different data types:Data TypeDefault Valueshort0int0long0Lfloat0.0fdouble0.0dchar'\u0000'

Question 18

Question 18Provide 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.

Accepted Answer

int xCoordinate = 0;  
int yCoordinate = 0;ORint xCoordinate = 0, yCoordinate = 0;

Question 19

Question 19Write 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.

Accepted Answer

double interestAmount = balanceAmount * rate;

Question 20

Question 20Explain the statement, "a well-documented code is as important as the correctly working code".

Accepted 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.

Values and Data Types