Question

State whether each of the following is true or false. If \(f\) a cain why. a) Comments cause the computer to print the text after the // on the screen when the program executes. b) All variables must be given a type when they are declared. c) Java considers the variables number and NuMbEr to be identical. d) The remainder operator ( \(\%\) ) can be used only with integer operands. c) The arithmetic operators \(", /, \$,+\) and \(-\) all have the same level of precedence.

Short answer

a) False b) True c) False d) False e) False

Step-by-step solution

Evaluate Comments Effect

For statement (a), evaluate whether comments in programming languages like Java affect program output. Comments, which typically start with `//` in Java, are ignored by the compiler and do not affect how the program runs or what it outputs. Thus, **(a) is false**.

Check Variable Declaration

For statement (b), assess if Java requires variables to have a type defined at declaration. Java is a statically typed language, meaning every variable must be defined with a type (e.g., `int`, `double`, `String`) when declared. Thus, **(b) is true**.

Compare Variable Names

For statement (c), compare case sensitivity in variable names in Java. Java is case-sensitive, so `number` and `NuMbEr` are considered different variables. Thus, **(c) is false**.

Review Remainder Operator Usage

For statement (d), evaluate if the remainder operator (`%`) can only work with integers. The `%` operator can be used with both integers and floating-point numbers to determine the remainder of a division operation. Thus, **(d) is false**.

Consider Operator Precedence

For statement (e), analyze the precedence of various arithmetic operators such as `*`, `/`, `%`, `+`, and `-`. In Java, `*`, `/`, and `%` have a higher precedence than `+` and `-`. Thus, **(e) is false**.

Key concepts

Comments in Java

Comments in Java are used to improve the readability of the code without affecting its actual execution. When you add comments using `//` for single-line comments or `/* ... */` for multi-line comments, they are purely for human readers.
The compiler ignores these comments, so they do not produce any output or affect how the program runs. They are handy for explaining what a particular piece of code does or to leave notes for future maintenance.

• Single-line comments start with `//`.
• Multi-line comments begin with `/*` and end with `*/`.

Understanding how to use comments effectively is crucial for good coding practices. Comments help with debugging and can be extremely useful when working in teams.

Variable Declaration and Types

In Java, when you declare a variable, you must specify its type. This is because Java is a statically typed language, which helps catch errors during the compile time rather than during runtime.
Common types include:

• `int` for integers like `5` or `-3`
• `double` for decimal numbers like `3.14`
• `String` for text, such as "Hello World"

This requirement ensures that the operations you perform on a variable make sense for its type. For example, you cannot perform arithmetic operations on `Strings` as you would with `ints` or `doubles`.
Understanding variable types and correctly declaring variables is fundamental for writing bug-free Java code.

Java Case Sensitivity

Java is a case-sensitive language. This means that variable names, method names, and other identifiers are distinct if their letter cases differ. For instance, variables named `example`, `Example`, and `EXAMPLE` are three different and independent variables.
This case sensitivity extends beyond variables to all identifiers such as class names, methods, and constants. It offers flexibility but can also lead to errors if not managed carefully.
Paying close attention to the case can prevent bugs and issues in your code and help maintain clarity, especially when dealing with different variables or identifiers that may have similar names.

Remainder Operator Usage

The remainder operator, represented by `%` in Java, is used to find the remainder of a division between two numbers. It can be applied not only to integers but also to floating-point numbers like `float` and `double`.
For example:

• `9 % 4` results in `1`, since 9 divided by 4 leaves a remainder of 1.
• `9.5 % 4.2` results in `1.1`, as it's suitable for floating-point operations.

The versatility of the remainder operator makes it useful in various calculations, especially when you need to determine even or odd numbers, or loop through collections cyclically.

Operator Precedence in Java

Operator precedence in Java determines how operators are parsed concerning each other. This is crucial for understanding how complex expressions are evaluated.
Arithmetic operators have different precedence levels. For example:

• Operators like `*`, `/`, and `%` have higher precedence than `+` and `-`.
• Expressions with operators of higher precedence are evaluated first.

To control the evaluation order, you can use parentheses. For instance, in the expression `3 + 2 * 5`, the multiplication occurs first due to higher precedence, resulting in `3 + 10`, which equals `13`.
Using parentheses like `(3 + 2) * 5` changes the evaluation order, leading to a result of `25`.