Podcast
Questions and Answers
Which of the following data types is a 64-bit floating point number?
Which of the following data types is a 64-bit floating point number?
- long
- float
- int
- double (correct)
Which naming convention is correct for class identifiers in Java?
Which naming convention is correct for class identifiers in Java?
- start with a lowercase letter and capitalized when necessary
- start with a capital letter and capitalize internal words (correct)
- all lowercase with underscores
- start with an underscore and letters only
What is the range of the byte data type in Java?
What is the range of the byte data type in Java?
- -128 to 127 (correct)
- -64 to 63
- -255 to 256
- -127 to 128
Which of the following is NOT a primitive data type in Java?
Which of the following is NOT a primitive data type in Java?
What is the correct way to declare a variable of type int with an initial value?
What is the correct way to declare a variable of type int with an initial value?
Which statement about boolean data types in Java is true?
Which statement about boolean data types in Java is true?
What is the primary difference between primitive data types and classes/objects in Java?
What is the primary difference between primitive data types and classes/objects in Java?
Which of the following is a valid identifier in Java?
Which of the following is a valid identifier in Java?
What occurs when casting is needed from a less inclusive data type to a more inclusive data type?
What occurs when casting is needed from a less inclusive data type to a more inclusive data type?
What will happen if the compiler encounters a necessary cast from a more inclusive to a less inclusive data type without explicit instruction?
What will happen if the compiler encounters a necessary cast from a more inclusive to a less inclusive data type without explicit instruction?
Which of the following examples will produce a syntax error?
Which of the following examples will produce a syntax error?
What defines a boolean expression in programming?
What defines a boolean expression in programming?
In the context of control structures, what is the purpose of using braces in if-else statements?
In the context of control structures, what is the purpose of using braces in if-else statements?
What is true about a Class in Java?
What is true about a Class in Java?
How should you name a Class in Java according to naming conventions?
How should you name a Class in Java according to naming conventions?
What is the purpose of the 'new' operator in Java?
What is the purpose of the 'new' operator in Java?
Which of the following is a built-in class in Java?
Which of the following is a built-in class in Java?
What does the 'import' statement achieve in Java?
What does the 'import' statement achieve in Java?
What can be concluded about object naming conventions in Java?
What can be concluded about object naming conventions in Java?
How do you access the behavior of an object once it is created in Java?
How do you access the behavior of an object once it is created in Java?
What will happen if a class is imported using 'import java.util.*'?
What will happen if a class is imported using 'import java.util.*'?
What is a unique feature of the String class in Java?
What is a unique feature of the String class in Java?
Which statement is true regarding print statements in Java?
Which statement is true regarding print statements in Java?
How do you declare a named constant in Java?
How do you declare a named constant in Java?
Which of the following represents a valid arithmetic operation in Java?
Which of the following represents a valid arithmetic operation in Java?
How does Java handle the conversion of primitive data types in expressions?
How does Java handle the conversion of primitive data types in expressions?
What is the purpose of the increment operator (++) in Java?
What is the purpose of the increment operator (++) in Java?
Which expression will result in integer division in Java?
Which expression will result in integer division in Java?
What is the default behavior of System.out.print() when called without arguments?
What is the default behavior of System.out.print() when called without arguments?
Study Notes
Identifiers
- Identifiers can be combinations of letters, digits, underscore (
_
) and dollar sign ($
) - They must start with a letter, underscore, or dollar sign.
- Avoid using the dollar sign - It can confuse the runtime system.
- It is best practice to start identifiers with a letter.
- Identifier conventions include:
- Variables and method names should be lowercase, with internal words capitalized (e.g.,
honkingBigVariableName
). - Constants should be all uppercase with underscores between internal words (e.g.,
ANOTHER_HONKING_BIG_INDENTIFIER
). - Classes names should start with a capital letter and use camel-case for internal words (e.g.,
HonkingLongClassName
).
- Variables and method names should be lowercase, with internal words capitalized (e.g.,
Data Types
- Primitive Data Types:
byte
,short
,int
,long
,float
,double
,boolean
,char
- Use
int
for integers anddouble
for real numbers.
- Use
- Classes and Objects:
- Pre-defined or user-defined data types containing constructors, methods, and fields.
- Fields (variables) can be primitive data types or objects.
Java Primitive Data Types
byte
: 8-bit signed integer, range: -128 to 127short
: 16-bit signed integer, range: -32768 to 32767int
: 32-bit signed integer, range: -2,147,483,648 to 2,147,483,647long
: 64-bit signed integer, range: -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807float
: 32-bit floating-point number, range: +1.4E-45 to +3.4028235E+38double
: 64-bit floating-point number, range: +4.9E-324 to +1.7976931348623157E+308boolean
: Representstrue
orfalse
- Java booleans cannot be converted to or from other data types.char
: 16-bit Unicode character, range:\u0000
to\uFFFF
. Can be mixed with integer types.
Classes and Objects
- Class is the blueprint for the data type.
- Object is an instance of a class - like a variable.
- Classes contain:
- Implementation details of the data type.
- Interface for programmers who want to use the data type.
- Objects have:
- Multiple pieces of internal data.
- Behaviors carried out via methods.
Name Conventions
- Java is case-sensitive.
- Class names start with a capital letter.
- All other names start with lowercase letters.
- Subsequent words are capitalized (e.g.,
theBigOne
). - Underscores are not used in names.
Creating and Using Objects
- Declaration:
DataType identifier
(e.g.,Rectangle r1;
) - Creation: Use the
new
operator and the constructor (e.g.,r1 = new Rectangle()
. - Behavior: Access methods through the dot operator (e.g.,
r2.setSize(10, 20);
).
Built-in Classes
- Java has a large library of built-in classes with various methods.
- Some examples include:
String
Math
Integer
,Character
,Double
System
Arrays
Scanner
File
Object
Random
Import Statement
- The
import
keyword enables the use of classes and packages from other parts of the code. - It does not import the code itself - this is handled by the compiler.
- Import statements are placed outside the class block, e.g.,
import java.util.ArrayList;
. - You can import a whole package:
import java.util.*;
- Or import specific classes:
import java.util.Random;
- The
java.lang.*
package is automatically imported in all classes, so you don't need to explicitly import classes within that package.
The String Class
String
is a standard Java class with many methods.- String literals exist,
String name = "Mike D.";
- String concatenation uses the
+
operator,String fullName = firstName + lastName;
Standard Output
- Use
System.out.print(expression);
to print without a newline. - Use
System.out.println(expression);
to print with a newline. - There is also just
System.out.println();
for printing only a newline.
Constants
- Literal Constants are values that remain constant throughout the program, e.g.,
true
,false
,null
,'c'
,"C++"
,12
,-12
,12.12345
. - Named Constants are declared with the
final
keyword and follow a naming convention.- Scope can be local to a method or to a class.
- Use named constants for any numerical constant besides
-1
,0
,1
, or2
. - e.g.,
final int NUM_SECTIONS = 3;
Operators
- Basic Assignment Operator:
=
- Arithmetic Operators:
+
,-
,*
,/
,%
(remainder) - Assignment Operators:
+=
,-=
,*=
,/=
,%=
- Increment and Decrement Operators:
++
,--
(prefix and postfix). Avoid using them within expressions.
Expressions
- Expressions are evaluated based on operator precedence.
- Java automatically converts numerical primitive data types, but results can be surprising, so be careful when mixing integer and floating point numbers in expressions.
- The meaning of an operator is determined by its operands (e.g.,
/
can be integer or floating point division).
Casting
- Casting is the temporary conversion of a variable from its original data type to another.
- Automatic casting occurs if a cast is necessary from a less inclusive data type to a more inclusive data type.
- e.g.,
double b = a * x + a / x;
- A cast from a more inclusive data type to a less inclusive data type requires explicit casting.
- Failure to do so results in a compile error.
- e.g.,
int y = (int) a / (int) b;
Primitive Casting Diagram (pg 19)
- The outer ring is the most inclusive data type.
- The inner ring is the least inclusive data type.
- Variables and sub-expressions of less inclusive data types are automatically cast to more inclusive types in expressions.
- Explicit casting is needed when an expression that is more inclusive must be placed into a variable that is less inclusive.
Java Control Structures
- Linear Flow of Control: Statements are executed consecutively, one after the other.
- Decision Making with
if-else
Statements: Allows execution of different blocks of code based on conditions.if(boolean-expression)
statement;
if(boolean-expression)
{
statement1;
statement2;
statement3;
}
- A statement within an
if
orelse
block can be replaced by a statement block enclosed in curly braces{}
, which can contain zero or more statements.
Boolean Expressions
- Evaluate to
true
orfalse
. - Relational Operators:
<
,>
,<=
,>=
,==
(equal to),!=
(not equal to) - Logical Operators:
&&
(AND),||
(OR),!
(NOT)
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Description
This quiz focuses on the rules and best practices for naming identifiers in programming, including variables, constants, and class names. Additionally, it covers the fundamental data types used in programming, from primitive types to classes and objects. Test your knowledge of these essential concepts in coding.