1. Lesson: Language Basics
  2. Variables
    1. Naming
    2. Primitive Data Types
    3. Default Values
    4. Literals
    5. Using Underscore Characters in Numeric Literals
    6. Arrays
    7. Declaring a Variable to Refer to an Array
    8. Creating, Initializing, and Accessing an Array
    9. Copying Arrays
    10. Summary of Variables
    11. Questions and Exercises: Variables
  3. Expressions, Statements, and Blocks
    1. Expressions
    2. Statements
    3. Blocks
    4. Questions and Exercises: Expressions, Statements, and Blocks
  4. Control Flow Statements
    1. The if-then Statement
    2. The if-then-else Statement
    3. The switch Statement
    4. Using Strings in switch Statements
    5. The while and do-while Statements
    6. The for Statement
    7. The break Statement
    8. The continue Statement
    9. The return Statement
    10. Summary of Control Flow Statements
    11. Questions and Exercises: Control Flow Statements
  5. Lesson: Classes and Objects
    1. Classes
    2. Declaring Classes
    3. Declaring Member Variables
    4. Access Modifiers
    5. Types
    6. Variable Names
    7. Defining Methods
    8. Naming a Method
    9. Overloading Methods
    10. Providing Constructors for Your Classes
    11. Passing Information to a Method or a Constructor
    12. Parameter Types
    13. Arbitrary Number of Arguments
    14. Parameter Names
    15. Passing Primitive Data Type Arguments
    16. Passing Reference Data Type Arguments
    17. Objects
    18. Creating Objects
    19. Declaring a Variable to Refer to an Object
    20. Instantiating a Class
    21. Initializing an Object
    22. Using Objects
    23. Referencing an Object's Fields
    24. Calling an Object's Methods
    25. The Garbage Collector
    26. More on Classes
    27. Returning a Value from a Method
    28. Returning a Class or Interface
    29. Using the this Keyword
    30. Using this with a Field
    31. Using this with a Constructor
    32. Controlling Access to Members of a Class
    33. Understanding Instance and Class Members
    34. Class Variables
    35. Class Methods
    36. Constants
    37. The Bicycle Class
    38. Initializing Fields
    39. Static Initialization Blocks
    40. Initializing Instance Members
    41. Summary of Creating and Using Classes and Objects
    42. Questions and Exercises: Classes
    43. Questions and Exercises: Objects
  6. Nested Classes
    1. Why Use Nested Classes?
    2. Static Nested Classes
    3. Inner Classes
    4. Inner Class Example
    5. Local and Anonymous Inner Classes
    6. Modifiers
    7. Summary of Nested Classes
    8. Questions and Exercises: Nested Classes
  7. Enum Types
    1. Questions and Exercises: Enum Types
  8. Annotations
    1. Documentation
    2. Annotations Used by the Compiler
    3. Annotation Processing
    4. Questions and Exercises: Annotations
  9. Lesson: Interfaces and Inheritance
    1. Interfaces
    2. Interfaces in Java
    3. Interfaces as APIs
    4. Interfaces and Multiple Inheritance
    5. Defining an Interface
    6. The Interface Body
    7. Implementing an Interface
    8. A Sample Interface, Relatable
    9. Implementing the Relatable Interface

3.1.Expressions #

An expression is a construct that is composed of variables, operators, and method invocations, and it evaluates to a single value in accordance with the syntax of the language. The following expressions are illustrated in bold below, as you have already seen examples:

int cadence = 0;
anArray[0] = 100;
System.out.println("Element 1 at index 0: " + anArray[0]);

int result = 1 + 2; // result is now 3
if(value1 == value2) 
     System.out.println("value1 == value2");

An expression, with its left-hand operand, determines the data type of the value returned. In Java programming, expressions can return a variety of values, including integers and boolean or string values. The data type of the left-hand operand is the same as the expression’s data type. Compound expressions can be generated from smaller expressions, provided the data type of one part matches that of the other. An illustration of a compound expression is as follows:

1 * 2 * 3

The order in which the expression is evaluated is irrelevant in this instance, as the result of multiplication is not affected by order; the outcome remains consistent regardless of the order in which the multiplications are applied. Nevertheless, this is not the case for all expressions. For instance, the results of the subsequent expression are contingent upon whether the addition or division operation is executed first:

x + y / 100 // ambiguous

Balanced parenthesis can be employed to specify the precise manner in which an expression will be evaluated: ( and ). For instance, the following could be written to ensure that the preceding expression is unambiguous:

(x + y) / 100 // unambiguous, recommended

The expression’s operator precedence determines the order of operations if you don’t specify it. High-priority operators are evaluated first. The division operator precedes the addition operator. Thus, these two statements are equivalent:

x + y / 100

x + (y / 100) // unambiguous, recommended

Write compound expressions with parentheses indicating which operators should be evaluated first. Code is easier to read and maintain with this practice.

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