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Questions and Answers
What must be avoided when naming identifiers in Java?
What must be avoided when naming identifiers in Java?
What is a defining feature of JavaDoc comments?
What is a defining feature of JavaDoc comments?
Which of the following correctly describes an end-of-line comment?
Which of the following correctly describes an end-of-line comment?
Which guideline is recommended for naming identifiers in Java?
Which guideline is recommended for naming identifiers in Java?
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What is a significant restriction when naming identifiers?
What is a significant restriction when naming identifiers?
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Which character sequence signifies the start of a block comment in Java?
Which character sequence signifies the start of a block comment in Java?
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What is a suggested practice for naming multi-word identifiers?
What is a suggested practice for naming multi-word identifiers?
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Which statement about Java keywords is true?
Which statement about Java keywords is true?
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What is a necessary requirement for Java program files?
What is a necessary requirement for Java program files?
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What do curly braces denote in a Java program?
What do curly braces denote in a Java program?
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What does a Java statement require at the end?
What does a Java statement require at the end?
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Which of the following is NOT a characteristic of comments in Java?
Which of the following is NOT a characteristic of comments in Java?
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What is the purpose of indentation in Java coding?
What is the purpose of indentation in Java coding?
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What is the role of the args variable in a Java program?
What is the role of the args variable in a Java program?
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Which of the following describes a block comment in Java?
Which of the following describes a block comment in Java?
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Which statement about Java statements is correct?
Which statement about Java statements is correct?
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Which method is used to indicate a long (64-bit) integer in Java?
Which method is used to indicate a long (64-bit) integer in Java?
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What is the appropriate way to declare a float literal in Java?
What is the appropriate way to declare a float literal in Java?
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Which of the following options correctly specifies an octal literal?
Which of the following options correctly specifies an octal literal?
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What are valid values for a Boolean literal in Java?
What are valid values for a Boolean literal in Java?
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How are string literals represented in Java?
How are string literals represented in Java?
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Which of the following represents a valid character literal?
Which of the following represents a valid character literal?
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Which statement about hexadecimal literals in Java is correct?
Which statement about hexadecimal literals in Java is correct?
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What is a common mistake when declaring a float literal?
What is a common mistake when declaring a float literal?
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Which of the following is NOT a primitive data type in Java?
Which of the following is NOT a primitive data type in Java?
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What is the initial value of a Boolean variable in Java?
What is the initial value of a Boolean variable in Java?
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How many characters can the char data type represent in Java?
How many characters can the char data type represent in Java?
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Which escape sequence correctly represents the trademark symbol (™) in Java?
Which escape sequence correctly represents the trademark symbol (™) in Java?
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Which of the following statements about the char data type is false?
Which of the following statements about the char data type is false?
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Which statement correctly describes the integer data types in Java?
Which statement correctly describes the integer data types in Java?
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Which sequence must begin with the characters '\u' to represent a Unicode character?
Which sequence must begin with the characters '\u' to represent a Unicode character?
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Which of the following is a characteristic of the Boolean data type in Java?
Which of the following is a characteristic of the Boolean data type in Java?
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What type should be used to represent the number of inhabitants of the planet?
What type should be used to represent the number of inhabitants of the planet?
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What is a key difference between Java and C regarding integer types?
What is a key difference between Java and C regarding integer types?
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Why is the double type usually preferred over float in applications?
Why is the double type usually preferred over float in applications?
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Which of the following prefixes indicates a hexadecimal number in Java?
Which of the following prefixes indicates a hexadecimal number in Java?
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What suffix is used to denote a float type in Java?
What suffix is used to denote a float type in Java?
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In what situations is it advisable to use the float type instead of double?
In what situations is it advisable to use the float type instead of double?
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Which of the following statements is false regarding floating-point representations in Java?
Which of the following statements is false regarding floating-point representations in Java?
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What must every variable in Java have?
What must every variable in Java have?
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Study Notes
Java Program Structure
- Program name: The name of the Java program is an identifier that should be the same as the filename.
-
Curly braces: Every Java program requires at least two pairs of curly braces: one surrounding the entire program and another surrounding the
main
method. -
args
variable: This is a placeholder for the command-line arguments that the program can receive.
Java Coding Guidelines
-
Filename: The filename of a Java program must match the public class name and end with
.java
. - Comments: Use comments for documentation and readability. They are ignored by the compiler.
- White spaces: White spaces (like spaces and tabs) are ignored by the compiler.
- Indentation: Indentation is for readability and helps organize the code.
Java Statements
-
Statement: A statement is one or more lines of code terminated by a semicolon (
;
). It represents an action to be performed during the program's execution. -
Block: A block is a group of statements enclosed within curly braces (
{}
). Blocks act as single units and replace statements within a program's structure. -
Comments: Comments are used for documentation and are ignored by the compiler.
-
Block comment: Begins with
/*
and ends with*/
. Used for multi-line descriptions. -
Line comment: Starts with
//
and continues until the end of the line. Used for single-line comments. -
JavaDoc comment: Starts with
/**
and ends with*/
. Used for documenting classes, attributes, and methods.
-
Block comment: Begins with
Identifiers
- Definition: Identifiers are names used by programmers to identify elements like classes, methods, and variables.
-
Naming rules:
- Must start with a letter, underscore
_
, or dollar sign$
. - Can contain letters, numbers, underscores, and dollar signs after the first character.
- Cannot be a Java keyword.
- Must start with a letter, underscore
-
Guidelines:
- Choose names that describe the purpose of the element.
- Use lowercase for method and variable names, uppercase for class names.
- Separate words in multi-word identifiers with underscores or by capitalizing the first letter of each word.
Java Keywords
- Definition: Keywords are reserved words that have specific meanings in the Java language. They cannot be used as identifiers.
-
Examples:
public
,class
,static
,void
,main
,String
,System
,out
,println
,int
,for
,while
,if
,else
Java Literals
- Definition: Literals are values that are directly represented in the code.
-
Integer literals:
- Decimal: Start with a non-zero digit and don't contain a decimal point.
- Octal: Start with a leading
0
. - Hexadecimal: Start with
0x
.
-
Floating-point literals: End with
F
orf
to indicatefloat
type. -
Boolean literals:
true
orfalse
. -
String literals: Enclosed in double quotes (
"
). Can contain escape sequences. -
Character literals: Enclosed in single quotes (
'
). Can contain escape sequences.
Data Types
- Simple types: Built-in, primitive data types.
- Composite types: Created by programmers using simple types, arrays, classes, and interfaces.
-
Primitive data types:
-
boolean
: Stores true or false values. -
char
: Stores single Unicode characters. -
byte
: Stores integers from -128 to 127. -
short
: Stores integers from -32,768 to 32,767. -
int
: Stores integers from -2,147,483,648 to 2,147,483,647 (most widely used). -
long
: Stores integers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. -
float
: Stores single-precision floating-point numbers (7 significant digits). -
double
: Stores double-precision floating-point numbers (15-16 significant digits).
-
Variables
- Definition: Variables are named locations in memory that store data.
- Components: Each variable has a data type and a name. The data type determines the kind of data the variable can hold.
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Description
This quiz covers the fundamental structure of a Java program, including naming conventions, the use of curly braces, and the args
variable. Additionally, it addresses coding guidelines such as comments, whitespace, indentation, and statements. Test your understanding of these essential Java concepts.