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Solutions for Computer Applications, Class 10, ICSE
Why does Java use the Unicode character set?
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.
What are escape sequences in Java? Give three examples.
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.
What is the result of evaluating the following expression?
(3 + 6 * 7) / 3 + 2
(3 + 6 * 7) / 3 + 2
⇒ (3 + 42) / 3 + 2
⇒ 45 / 3 + 2
⇒ 45 / 3 + 2
⇒ 15 + 2
⇒ 17
What is a token in Java? Name the tokens available in Java.
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.
Why can a keyword not be used as a variable name?
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.
Which of the following are Java keywords?
area, input, class, public, int, x, y, radius, long, Hello java
class, public, int, long are Java keywords.
What are identifiers in Java? List three identifier formation rules.
Identifiers are used to name different parts of a program such as variables, methods, classes, objects, etc. Three identifier formation rules are:
Explain the following statement — "In Java, total, Total, ToTaL, and TOTAL are all different identifiers."
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.
Which of the following are invalid identifiers?
i. ten
ii. "Hello"
iii. 5678
iv. Coffee
v. $dollar
vi. 4Variables
vii. _var
How would you print characters like \, ' and " in Java?
We can print characters like \, ' and " using escape sequences i.e. preceding it with a backslash (\) symbol.
Distinguish between the following:
i. Token and Identifier
| Token | Identifier |
|---|---|
| Each 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 Identifier
| Keyword | Identifier |
|---|---|
| Keywords 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 Constant
| Character Constant | String Constant |
|---|---|
| Character 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 Constant
| Integer Constant | Float Constant |
|---|---|
| Integer 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, char | Float Constants are assigned to variables of data type — float, double |
Distinguish between "A" and 'A'.
"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.
What is wrong with the following statement?
float flt = 7895.0345;
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;
Describe primitive data types in Java.
Primitive data types are fundamental data types that are an integral part of the Java language and are used to declare a variable.
List the size of primitive data types in Java.
| Data Type | Size in Bytes |
|---|---|
| byte | 1 |
| short | 2 |
| int | 4 |
| long | 8 |
| float | 4 |
| double | 8 |
| char | 2 |
| boolean | 1 |
Which integer and floating point data types take up the same number of bits in computer memory?
Both, int and float take up 32 bits in memory. Similarly, both long and double take up 64 bits in memory.
What is variable initialisation in Java? What are the default values of the following type of variables? short, int, long, float, double, and char.
Variable initialisation means assigning value to a variable for the first time. Below are the default values of the different data types:
| Data Type | Default Value |
|---|---|
| short | 0 |
| int | 0 |
| long | 0L |
| float | 0.0f |
| double | 0.0d |
| char | '\u0000' |
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.
int xCoordinate = 0;
int yCoordinate = 0;OR
int xCoordinate = 0, yCoordinate = 0; 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.
double interestAmount = balanceAmount * rate;Explain the statement, "a well-documented code is as important as the correctly working code".
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.
How can you write single line comments in Java?
Single line comments in Java can be written using //. For example:
// This is an example of single line comment.Write a Java constant declaration that gives the name TAX_RATE to the value 15%.
final int TAX_RATE = 15;If you want to change the precedence of operations in an expression, which symbols do you use?
Brackets — () can be used to change operator precedence.
What are symbolic constants? How are they useful in writing programs?
Memory locations whose values cannot be changed within a program are called constants or symbolic constants. The advantages of symbolic constants are:
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);Below is the output produced by this code:
y
z
zVariable 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.
Java uses ........... character set.
ASCII stands for ...........
ASCII is ...........
Extended ASCII is ...........
The smallest individual component in a program is called ...........
Which of the following is not a token?
Which of the following is a keyword?
Which of the following is not a legal identifier?
Which of the following is a default value of float data type?
Which of the following is a default value of boolean data type?
Which of the following is an invalid integer?
Which of the following is not a character literal?
Which of the following punctuator is the statement terminator in Java?
Which of the following is not a primitive data type in Java?
What is the size of a long data type in Java?
What is the size of a boolean data type in Java?
Single line comments can be added using ...........
Which of the following changes a variable declaration into a constant?
The ASCII codes of A-Z are represented by decimal range ...........
Which of the following is a primitive data type?
Java supports the use of the ASCII character set only.
False
The ASCII code for character 'Z' is 90.
True
The smallest unit in a Java program is known as token.
True
The Unicode character set uses 8 to 32 bits per character.
True
In an escape sequence, a character is preceded by a backward slash (\).
True
In Java, an identifier can begin with a $ sign.
True
The boolean data type is used for storing logical values.
True
Java offers five types of tokens.
True
Identifiers in Java may be of any length.
True
The char data type reserves 8 bits in memory.
False
Default value of reference data type is null.
True
To designate a literal constant of the type float, you must append the letter L to it.
False
Default value of char data type is '\u0000'.
True
If a literal constant contains a decimal point, then it is of the type double by default.
True
A variable can be used in a Java program even if it has not been declared.
False