Mod 2: Comp Prog

55問 • 1年前

問題一覧

are tokens that represent names of variables, methods, classes, and other user-defined program elements. All Java variables must be identified with unique names.

Identifiers

Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume). It is recommended to use descriptive names in order to create understandable and maintainable code.

True

The general rules for constructing names for an identifier (unique identifiers) are: Identifiers must begin with either a letter, an underscore “_”, or a dollar sign “$”. Letters may be lower or upper case. Subsequent characters may use numbers 0 to 9.

True

Identifiers cannot use Java keywords like class, public, void, etc.

True

Java Identifiers Best Practices For names of classes

AnExampleOfClassName

Java Identifiers Best Practices: For names of methods and variables

anExampleOfMethodName

Java Identifiers Best Practices: For names of constant

EXAMPLE_OF_A_CONSTANT

Avoid using underscores at the start of the identifier such as _read or _write.

true

is an item of data used to store the state of objects.

Variable

determines the type of value that the variable can hold.

Data Type

Name The variable name must follow rules for identifiers.

True

is an attribute of data which tells the compiler or interpreter how the programmer intends to use the data.

Data Type

Data types are divided into two groups: Primitive data types Non-primitive data types

True

specifies the size and type of variable values, and it has no additional methods.

Primitive Data Type

Stores whole numbers, positive or negative (such as 123 or -456), without decimals. Valid types are byte, short, int and long. Which type you should use, depends on the numeric value.

Integer types

can store whole numbers from -128 to 127. This can be used instead of int or other integer types to save memory when you are certain that the value will be within -128 and 127.

Byte

can store whole numbers from -32,768 to 32,767.

Short

can store whole numbers from -2,147,483,648 to 2,147,483,647. In general, the int data type is the preferred data type when we create variables with a numeric value.

Int

type can store whole numbers from 9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. This is used when int is not large enough to store the value.

Long

Represents numbers with a fractional part, containing one or more decimals.

Floating point Type

What are the two tyoes of floating data types:

Float & double

can store fractional numbers from 3.4e−038 to 3.4e+038.

Float

can store fractional numbers from 1.7e−308 to 1.7e+308.

Double

The “precision of float” is only six(6) or seven(7) decimal digits, while “double variables” have a precision of about “15 digits”. Therefore it is safer to use double for most calculations.

True

type is declared with the boolean keyword and can only take the values true or false.

Boolean

type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c':

Character

types are called reference types because they refer to objects.

Non - Primitive Data Types

Examples of non-primitive types are Strings, Arrays, Classes, Interface, etc.

True

type is used to store a sequence of characters (text). String values must be surrounded by double quotes.

Strings

is a statement that can convey a value. Some of the most common are mathematical, such as in the following source code example: int number = 4; int anotherNumber = number; int product = number * anotherNumber;

Expressions

is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Java is rich in built-in operators and provide the following types of operators: 1. Unary Operators 2. Arithmetic operators 3. Assignment operators 4. Relational operators 5. Logical operators

Operators

are used with only one operand.

Unary Operators

are used to perform common mathematical operations.

Arithmetic operators

are used to assign values to variables.

Assignment Operators

used to check the relationship between two operands.

Relational operators

are used to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0.

Logical Operators

this line of code correct? System.out.println("The area is " + String.format(%.2f, area) + ".");

False

Solve this expression, is the answer correct? int answer; answer = 50 * 2 - 15 / 3 + 10 % 2 + 6; System.out.print(answer); The answer is 101.

True

Solve the expression, is the answer correct? double number; number = 20 / 2 * 4 - 2 + 10 - (-2); System.out.println(number); 50

False

Solve the expression, is the answer correct? int number; number = 10 - 4 + 8 / 4 * 2; System.out.println(number); The answer is 10.

true

Solve the expression, is the answer correct? double number; number = 40 - 10 / 5 * 6 / 3 + 100 / 2; System.out.println(number); The answer is 86.

False

Solve this expression, is the answer correct? int answer; answer = 40 - 10 / 5 * 6 / 3 + 100 / 2; System.out.print(answer); The answer is 76.

False

Is this a best practice and recommended code for declaration? int inputNumber;

True

There are no errors in this code snippet. if(age >= 18) { System.out.print("Adult"); } else { System.out.print("Minor"); }

True

Solve the expression, is the answer correct? double number; number = 50 + 10 / 5 * 6 / 2 + 100; System.out.println(number); The answer is 156.0

True

Is this a best practice and recommended code for declaration of variable? int secondInput;

True

Is this a best practice and recommended code for a class name? PrimeNumbers

True

Is this a valid variable name? number1

true

Is this line of code correct? System.out.println("I love Java\nprogramming.\n");

true

Is this line of code correct? public Static void main(String[] args) { }

False

int answer; answer = 30 - 20 / 10 / 3 + 100 / 2; System.out.println(answer); The answer is 80.

True

Is this line of code correct? length = input.nextFloat();

True

double answer; answer = 12 - 20 / 4 + 10 % 2 + 6 % 2 - 1; System.out.println(answer); The answer is 6.0double answer; answer = 12 - 20 / 4 + 10 % 2 + 6 % 2 - 1; System.out.println(answer); The answer is 6.0

True

Is this line of code correct? if(console.hasNextDouble() == true):

False

Is this a valid variable name? _option

True

Data Structure (history)

iam noone · 64問 · 1年前

Data Structure (history)