© 2007 Lawrenceville Press Slide 1 Chapter 4 Assignment Statement An assignment statement gives a...

© 2007 Lawrenceville PressSlide 1

Chapter 4Chapter 4

Assignment StatementAssignment StatementChapter 4Chapter 4

Assignment StatementAssignment 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


Chapter 4Chapter 4

Variable AssignmentVariable AssignmentChapter 4Chapter 4

Variable AssignmentVariable Assignment

A variable can store only one value at any time.

int x;x = 5;x = 10;

xx

510


Chapter 4Chapter 4

Primitive Data TypesPrimitive Data TypesChapter 4Chapter 4

Primitive Data TypesPrimitive Data Types

Type Storage Requiredint 4 bytesdouble 8 byteschar 2 bytesboolean 1 bit


Chapter 4Chapter 4

Abstract Data TypesAbstract Data TypesChapter 4Chapter 4

Abstract Data TypesAbstract Data Types

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

Circle spot = new Circle(4);spotspot

getRadius()area()


Chapter 4Chapter 4

Java PackagesJava PackagesChapter 4Chapter 4

Java PackagesJava Packages

Numerous packages are included with JDK

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.


Chapter 4Chapter 4

The Scanner ClassThe Scanner ClassChapter 4Chapter 4

The Scanner ClassThe Scanner Class

Part of the java.util package

A Scanner object processes text and numbers from the input stream

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


Chapter 4Chapter 4

Integer DivisionInteger DivisionChapter 4Chapter 4

Integer DivisionInteger Division

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


Chapter 4Chapter 4

Real DivisionReal DivisionChapter 4Chapter 4

Real DivisionReal 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


Chapter 4Chapter 4

Modulus DivisionModulus DivisionChapter 4Chapter 4

Modulus DivisionModulus Division

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


Chapter 4Chapter 4

Operator PrecedenceOperator PrecedenceChapter 4Chapter 4

Operator PrecedenceOperator 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


Chapter 4Chapter 4

Changing the Order of Changing the Order of OperationsOperations

Chapter 4Chapter 4

Changing the Order of Changing the Order of OperationsOperations

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


Chapter 4Chapter 4

Type CastingType CastingChapter 4Chapter 4

Type CastingType 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


Chapter 4Chapter 4

Assignment OperatorsAssignment OperatorsChapter 4Chapter 4

Assignment OperatorsAssignment Operators

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

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

assignment


Chapter 4Chapter 4

Named ConstantsNamed ConstantsChapter 4Chapter 4

Named ConstantsNamed 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.


Chapter 4Chapter 4

Java KeywordsJava KeywordsChapter 4Chapter 4

Java KeywordsJava 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 trycontinue implements return voiddefault import short volatiledo instanceof static While


Chapter 4Chapter 4

Programming ErrorsProgramming ErrorsChapter 4Chapter 4

Programming ErrorsProgramming 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.


Chapter 4Chapter 4

Flowchart SymbolsFlowchart SymbolsChapter 4Chapter 4

Flowchart SymbolsFlowchart Symbols

processprocess


Chapter 4Chapter 4

The BirthdayGame FlowchartThe BirthdayGame FlowchartChapter 4Chapter 4

The BirthdayGame FlowchartThe BirthdayGame Flowchart

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