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Questions and Answers
Which of the following is considered a legal identifier in Java?
Which of the following is considered a legal identifier in Java?
Which naming convention is used for class names in Java?
Which naming convention is used for class names in Java?
What is the primary purpose of reserved keywords in Java?
What is the primary purpose of reserved keywords in Java?
Which of the following statements about variable declaration is true?
Which of the following statements about variable declaration is true?
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Which symbol is used as the assignment operator in Java?
Which symbol is used as the assignment operator in Java?
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What is the role of whitespaces in Java code?
What is the role of whitespaces in Java code?
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Which of the following is NOT a reserved keyword in Java?
Which of the following is NOT a reserved keyword in Java?
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What is the purpose of using camel case in naming identifiers in Java?
What is the purpose of using camel case in naming identifiers in Java?
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What defines a Java token?
What defines a Java token?
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Which escape sequence is used to create a tab space in Java?
Which escape sequence is used to create a tab space in Java?
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Which statement correctly describes a valid identifier in Java?
Which statement correctly describes a valid identifier in Java?
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How does a single-line comment begin in Java?
How does a single-line comment begin in Java?
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Which of the following escape sequences represents a newline character in Java?
Which of the following escape sequences represents a newline character in Java?
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What is the purpose of curly braces {} in Java?
What is the purpose of curly braces {} in Java?
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Which of these is NOT a rule for naming identifiers in Java?
Which of these is NOT a rule for naming identifiers in Java?
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Which symbol marks the end of a complete programming statement in Java?
Which symbol marks the end of a complete programming statement in Java?
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Which of the following components must always be present in a Java application?
Which of the following components must always be present in a Java application?
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What is the purpose of comments in Java?
What is the purpose of comments in Java?
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Which statement about the print and println methods is true?
Which statement about the print and println methods is true?
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Which of the following is a valid identifier in Java?
Which of the following is a valid identifier in Java?
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What happens if you incorrectly format a class header in Java?
What happens if you incorrectly format a class header in Java?
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In which of the following scenarios is a single-line comment used?
In which of the following scenarios is a single-line comment used?
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Which of the following is NOT a type of comment in Java?
Which of the following is NOT a type of comment in Java?
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What is the correct use of escape sequences in Java strings?
What is the correct use of escape sequences in Java strings?
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Study Notes
Java Fundamentals
- Java programs use comments, ignored by the compiler.
- Comments start with
//(single line) or/* */(multiple lines). - A class header contains an access modifier (e.g.,
public), theclasskeyword, and the class name (e.g.,Student). - Curly braces
{}define the scope of a class or method.
Parts of a Java Program
- Every Java application needs a
mainmethod. - The
mainmethod executes the program. - Java statements within the
mainmethod run sequentially when the program is executed. - Class headers, method headers and curly braces do not end with a semicolon.
-
System.out.println()is used to print output.
Console Output
- Java output is handled through the Java API (Application Programming Interface).
- The API is a prewritten library of classes for operations.
-
System.out.print()will print data to the console. -
System.out.println()will print the data and move the cursor to the next line. -
Systemis a part of the Java API. -
println()prints data then advances the cursor to the next line. -
print()prints data without advancing the cursor.
Comments
- Comments are for human readers; the compiler ignores them.
- Comments come in single-line
//and multi-line/* */. -
Javadoccomments (/** */) help document code.
Java Tokens
- Tokens are the smallest units of a Java program.
- Examples include keywords (
int,double,class,public), operators (+,-), symbols ({,}), constants, and identifiers.
Special Characters
-
//: Single-line comment -
(): Parentheses in method headers for parameter lists. -
{}: Curly braces to enclose code sections. -
"": Quotation marks for strings -
;: Semicolon to end a statement.
Java Escape Sequences
- Escape sequences start with
\and specify special characters. -
\n: Newline -
\t: Tab -
\b: Backspace -
\r: Carriage return -
\\: Backslash -
\': Single quote -
\": Double quote
Identifiers
- Identifiers are names used for variables, constants, classes, and methods.
- Identifiers consist of letters, digits, underscore (
_), and dollar sign ($). - Identifiers cannot start with a digit.
- Java is case-sensitive (
Numberis different fromnumber). - Reserved keywords cannot be used as identifiers (e.g.,
int,class,void).
Naming Conventions
- Identifiers should be descriptive and self-documenting.
- Use lower camel case for variable names (e.g.,
studentName). - Use upper camel case for class names (e.g.,
Student). - Avoid run-together words. Use underscores if necessary (e.g.,
annual_sale).
Reserved Words (Keywords)
- Reserved words, also called keywords, have specific meanings in Java and cannot be redefined.
- Examples:
int,short,float,double,char,final,void,return.
Whitespaces
- Java programs use whitespace to separate elements (e.g., words, symbols).
- Whitespace includes spaces, tabs, and newlines.
- Spaces, tabs, and newlines are used for readability.
Variables
- Variables are named memory locations whose contents can be changed.
- Variables are accessed using their names.
Variable Declaration
- Declare variables by specifying the data type and identifier.
- Example:
int count;,double price;,String name;
Assignment Statement
- Variables get values using the assignment operator (
=). - Example:
age = 30;
Example: Variable Initialization
- Initialize variables at declaration or later.
- Example:
int age = 30;,String name = "Alice";
Example: Printing variable Value
- Print the value of variables using
println(). - Example:
System.out.println(age);
Credit
- Tony Gaddis's "Starting Out with Java: From Control Structures through Objects" (6th Edition)
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Description
Test your knowledge on the fundamentals of Java programming! This quiz covers essential topics such as comments, class headers, and the main method. Challenge yourself to see how well you understand the core concepts of Java.
