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