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Questions and Answers
What is the output of the code System.out.println(Math.pow(2, 3));?
What is the output of the code System.out.println(Math.pow(2, 3));?
- 8.0 (correct)
- 16
- 9
- 6
What is a number literal in Java?
What is a number literal in Java?
- A keyword that represents a data type.
- A variable that stores a numerical value.
- A constant value that appears directly in the program. (correct)
- A mathematical operation.
What is the data type of the literal 5.0 in Java?
What is the data type of the literal 5.0 in Java?
- float
- long
- double (correct)
- int
What does the method System.currentTimeMillis() return?
What does the method System.currentTimeMillis() return?
What is the main difference between the ++i and i++ operators?
What is the main difference between the ++i and i++ operators?
What does type casting in Java refer to?
What does type casting in Java refer to?
What is the data type of a variable that can store a single character?
What is the data type of a variable that can store a single character?
What is the purpose of the Character.isDigit() method?
What is the purpose of the Character.isDigit() method?
Flashcards
Math.pow(2, 3) output
Math.pow(2, 3) output
The Java method Math.pow(base, exponent) calculates base raised to the power of exponent. In this case, 2 raised to the power of 3 is 8.0
Number literal in Java
Number literal in Java
A fixed value that appears directly in the program, not stored in a variable.
Data type of 5.0
Data type of 5.0
The data type of the literal 5.0 in Java is double.
System.currentTimeMillis()
System.currentTimeMillis()
Gets the current time in milliseconds since the Unix epoch.
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++i vs i++
++i vs i++
++i increments i before use, while i++ increments i after use.
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Type casting in Java
Type casting in Java
Converting a variable from one data type to another.
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int(3.9)
int(3.9)
Casting a floating-point value to an integer truncates the decimal part (rounds down).
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Random integer (1-10)
Random integer (1-10)
Generating a random integer within a specific range.
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Character data type
Character data type
The data type char stores a single character.
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Unicode
Unicode
A character encoding scheme that assigns unique numerical values to characters.
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Escape sequence
Escape sequence
A sequence of characters representing a special character in a string.
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Character.isDigit()
Character.isDigit()
Checks if a given character is a digit.
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String data type
String data type
Stores a sequence of characters.
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String.length()
String.length()
Returns the number of characters in a string.
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Java Variables and Data Types
- Variable Declaration: Used to store values in a program.
- Number Literal: A constant numerical value appearing directly in the code. Not a variable.
Math.pow(2, 3)Output: 8.05.0Data Type:doubleSystem.currentTimeMillis()Purpose: Gets the current time in milliseconds since the Unix epoch.- Increment Operators (
++ivsi++):++iincrements the value before use,i++after.
Java Operators and Expressions
- Type Casting: Converting a variable from one data type to another.
int i = (int)3.9;Output 3 (integer truncation)
Java Random Numbers and Characters
- Random Integer (1-10): Methods exist for this but are not detailed.
- Character Data Type:
char - Unicode: A 16-bit character encoding scheme.
- Escape Sequence: A sequence of characters representing a special character (e.g., newline).
Character.isDigit()Purpose: Checks if a character is a digit.- String Data Type:
String String.length()Purpose: Retrieves the length (number of characters) of a string.String.charAt()Purpose: Returns the character at a specific index in a string.String.concat()Purpose: Concatenates (joins) two strings.
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