slide 1 chapter 4 assignment statement an assignment statement gives a value to a variable....

Slide 1

Chapter 4

Assignment StatementChapter 4

Assignment Statement

An assignment statement gives a value to a variable.

Assignment can take several forms:

x = 5; a literal (5) is assigned to x

x = y + 2; the value of an expression (y + 2) is assigned to x

x = z; the value of another variable (z) is assigned to x

Slide 2

Chapter 4

Variable AssignmentChapter 4

Variable Assignment

A variable can store only one value at any time.

int x;x = 5;x = 10;

x

510

Slide 3

Chapter 4

Primitive Data TypesChapter 4

Primitive Data Types

Type Storage Requiredint 4 bytesdouble 8 byteschar 2 bytesboolean 1 bit

Slide 4

Classic Asteroids Gamefrom Atari

Classic Asteroids Gamefrom Atari

Slide 5

A variable declared with a class is called an object. For example, the object a47 is type Asteroid:

Asteroid a47 = new Asteroid();

a47a47.setLocation(x,y)a47.destroy()

Slide 6

Chapter 4

Java PackagesChapter 4

Java Packages

Numerous packages are included with JRE (Java Runtime Environment)

Packages contain classes

Packages can be added to an application with an import statement. For example, the statement

import java.util.Scanner;

makes the Scanner class and its methods accessible to the application.

Slide 7

Chapter 4

The Scanner ClassChapter 4

The Scanner Class

Part of the java.util packageimport java.util.*;

A Scanner object processes text and numbers from the input stream

Methods include:next()nextLine()nextInt()nextDouble()nextBoolean()close()

Slide 8

Chapter 4

Integer DivisionChapter 4

Integer Division

Integer division (/) is performed when both operands are integers. Only the integer portion of the quotient is returned:

int answer;answer = 20 / 7;System.out.print(answer);

Output

2

Source Code

Slide 9

Chapter 4

Real DivisionChapter 4

Real Division

Real division (/) is performed when one or both operands are type double. The entire quotient, including the decimal portion is returned:

double result;result = 20.0/7.0; //result is 2.857

Slide 10

Chapter 4

Modulus DivisionChapter 4

Modulus Division

Modulus division (%) returns the remainder of a division operation:

int answer;answer = 20 % 7;System.out.print(answer);

Output

6

Source Code

Slide 11

Chapter 4

Operator PrecedenceChapter 4

Operator Precedence

Operators in Java have the following precedence:

1. multiplication and division

2. addition and subtraction

Operators of the same precedence are evaluated in order from left to right. For example, multiplication is performed first, then division, and finally addition:

5 + 6 * 4 / 2 = 17

Slide 12

Chapter 4

Changing the Order of Operations

Chapter 4

Changing the Order of Operations

The order in which operators are evaluated can be changed by using parentheses. For example, addition is performed first, then multiplication, and finally division:

(5 + 6) * 4 / 2 = 22

Slide 13

Chapter 4

Type CastingChapter 4

Type Casting

Assigning an integer value into a floating-point variable works just fine. For example:

double bankAccountBalance = 1000;

However assigning a floating-point value into an integer variable is like trying to fit a large object in a small box.

By default, Java treats it as an illegal operation. For example, this causes an error:

int temperature = 22.8;

Slide 14

Chapter 4

Type CastingChapter 4

Type Casting

Type Casting converts a number of one type to a number of a different, but compatible type. Type casting is used to:

1. make the operand types in an expression match. For example, wholeNum = (int)y * 2

2. truncate the decimal portion of a double. For example, wholeNum = (int)z

3. change the way in which a division (/) operation will be performed. For example, realDivision = (double)a / (double)b

Slide 15

Chapter 4

Assignment OperatorsChapter 4

Assignment Operators

Operator Operation+= addition and then assignment-= subtraction and then assignment*= multiplication and then

assignment/= division and then assignment%= modulus division and then

assignment

Slide 16

Chapter 4

Named ConstantsChapter 4

Named Constants

A named memory location that cannot be changed from its initial value.

The keyword final is used in a constant declaration.

Constant identifiers are typically all uppercase with an underscore (_) separating words within the identifier name.

Slide 17

Chapter 4

Java KeywordsChapter 4

Java Keywords

abstract double int strictfpboolean else interface superbreak extends long switchbyte final native synchronizedcase finally new thiscatch float package throwchar for private throwsclass goto protected transientconst if public try

continue implements return voiddefault import short volatile

do instanceof static while

Slide 18

Chapter 4

Programming ErrorsChapter 4

Programming Errors

Syntax errors violate the rules of Java.

Logic errors, also called semantic errors, occur in statements that are syntactically correct, but produce undesired or unexpected results.

Run-time errors, also called exceptions, halt program execution at the statement that cannot be executed. One type of exception is called InputMismatchException.

Slide 19

Chapter 4

Flowchart SymbolsChapter 4

Flowchart Symbols

process

Slide 20

Chapter 4

The BirthdayGame FlowchartChapter 4

The BirthdayGame Flowchart