MELJUN CORTES's - Java Numerical Data Types & Expressions

8/9/2019 MELJUN CORTES's - Java Numerical Data Types & Expressions

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MELJUN CORTES MBA MPA BSCS ACSMELJUN CORTES MBA MPA BSCS ACS

Chapter 3

Numerical Data


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MELJUN CORTES,MBA,MPA,BSCS,ACSMELJUN CORTES,MBA,MPA,BSCS,ACS

Chapter 3 Objectives

After you have read and studied thischapter, you should be able to

Select proper types for numerical data.

Write arithmetic expressions in Java.

Evaluate arithmetic expressions, using theprecedence rules.

Describe how the memory allocationworks for objects and primitive datavalues.


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Chapter 3 Objectives, cont.

After you have read and studied thischapter, you should be able to

Write mathematical expressions, using

methods in the Math class.

Use the GregorianCalendarclass in

manipulating date information such as year,

month, and day.

Use the DecimalFormat class to format

numerical data.


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Chapter 3 Objectives, cont.

After you have read and studied thischapter, you should be able to Convert input string values to numerical

data.

Apply the incremental developmenttechnique in writing programs.

(Optional) Describe how integers and real

numbers are represented in memory.

Input data by using System.in and outputdata using System.out.


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3.1 Variables

To compute the sum and the differenceofx and y in a program, we must first

declare what kind of data will be

assigned to them.

After we assign values to them, we can

compute their sum and difference.


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3.1 Variables

When a declaration, such asint x,y;

is made, memory locations to store datavalues forx and y are allocated.

These memory locations are calledvariables, and x and y are the names

we associate with the memorylocations.


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3.1 Variables

A variable has three properties: A memory location to store the value.

The type of data stored in the memory

location.

The name used to refer to the memorylocation.


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3.1 Variables

The syntax for declaring variables is ;

where is a sequence of

identifiers separated by commas.

Every variable we use in a program

must be declared.


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3.1 Variables

There are six numerical data types inJava: byte

short

int

long

float

double

Data types byte, short, int, and longare for integers.

Float and double are for real numbers.


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3.1 Variables

At the time a variable is declared, it canalso be initialized.

int count = 10, height = 34;

We assign a value to a variable by

using an assignment statement.

Do not confuse mathematical equalityand assignment. The following is not

valid Java code:

4 + 5 = x;


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3.1 Variables

The only difference between a variablefor numbers and a variable for objects

is the contents in the memory

locations.

For numbers, a variable contains thenumerical value itself.

For objects, a variable contains an

address where the object is stored.


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Fig. 3.1

A diagram showing how two memorylocations (variables) are declared, and

values are assigned to them.


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Fig. 3.2

A difference between object declarationand numerical data declaration.


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3.1 Variables

We use the new command to create anobject.

Objects are called reference data types,

because the contents are addressesthat refer to memory locations where

the objects are actually stored.

Numerical data are calledprimitive data

types.


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Fig. 3.3

An effect of assigning the content of onevariable to another.


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3.2 Arithmetic Expressions

Arithmetic operators in Java


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An illustration of a subexpression in theexpression x + 3 * y


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Precedence rules for arithmeticoperators and parentheses


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Rules for arithmetic promotion


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3.3 Constants

If we want a variable to remain fixed, weuse a constant.

A constant is declared in a manner similar

to a variable, but with the additionalreserved word final.

final double PI = 3.14159;final int MONTHS_IN_YEAR = 12;


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3.3 Constants

If a literal constant contains a decimalpoint, it is of type double by default.

To designate a literal constant of type

float, append a letter f or F to thenumber:

2 * PI * 345.79F


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3.3 Constants

Numbers in scientific notation, such asNumber x 10exponent

are expressed in Java using the syntax E

12.40e+209

29.009E-102


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3.4 Getting Numerical Input Values

Wrapper classes are used to performnecessary type conversions, such as

converting a String object to a

numerical value.


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/*

Chapter 3 Sample Program: Compute AreaandCircumference

File: Ch3Circle.java

*/

import javax.swing.*;

import java.text.*;

class Ch3Circle {

public static void main( String [] args ) {

finaldouble PI = 3.14159;

String radiusStr;


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doubleradius,area, circumference;

radiusStr =JOptionPane.showInputDialog(null, "Enterradius:");

radius = Double.parseDouble(radiusStr);

//computeareaand circumferencearea = PI * radius * radius;

circumference = 2.0 * PI * radius;

JOptionPane.showMessageDialog(null, "GivenRadius: " + radius + "\n" + "Area: "+ area + "\n" + "Circumference: " +circumference);

}

}


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An illustration of how the compilerinterprets an overloaded operator.

int x = 1;

int y = 2;String output = test + x + y;

String output = x + y + test;


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Fig. 3.4

The dialog that appears when the inputvalue 2.35 was entered into the

Ch3Circle program.


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Fig. 3.5

The result of formatting the outputvalues by using a DecimalFormat

object.


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3.5 Standard Output

The showMessageDialog method isintended for displaying short one-line

messages, not for a general-purpose

output mechanism.

Using System.out, we can output

multiple lines of text to the standard

output window.


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Fig. 3.6

The standard output window fordisplaying multiple lines of text.


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3.5 Standard Output

We use the print method to output avalue.

The print method will continue printing

from the end of the currently displayedoutput.


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Fig. 3.7

Result of executingSystem.out.print(Hello, Dr.

Caffeine.).


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Fig. 3.8

Result of sending five print messagesto System.out of Figure 3.7.


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3.5 Standard Output

The print method will do the necessarytype conversion if we pass numerical

data.

We can print an argument and skip tothe next line so that subsequent output

will start on the next line by using

println instead ofprint.


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Fig. 3.9

The result of mixing print with fourprintln messages to System.out.


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3.6 Standard Input

The technique of using System.in toinput data is called standard input.

We can only input a single byte using

System.in directly.

To input primitive data values, we usethe Scanner class (from Java 2 SDK

1.5).


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Here's a sample code to input oneinteger and one double:

Scanner scanner;

scanner = Scanner.create(System.in);

int num = scanner.nextInt();

double val = scanner.nextDouble();


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Method Example

nextByte( ) byte b = scanner.nextByte( );

nextDouble( ) double d = scanner.nextDouble( );nextFloat( ) float f = scanner.nextFloat( );

nextInt( ) int i = scanner.nextInt( );

nextLong( ) long l = scanner.nextLong( );

nextShort( ) short s = scanner.nextShort( );

next() String str = scanner.next();

Common Methods:


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3.7 The Math Class

The Math class in thejava.langpackage contains class methods for

commonly used mathematical

functions.

Table 3.6 contains a partial list of class

methods available in the Math class.


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3.8 The GregorianCalendarClass

The GregorianCalendarclass is usefulin manipulating calendar information

such as year, month, and day.

Note that the first month of the year,January, is represented by 0.


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Fig. 3.12

Result of running the Ch3TestCalendarprogram at November 11, 2002, 6:13

p.m.


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3.9 Sample Development: Loan Calculator

Program flow: Get three input values:

loanAmount, interestRate, and

loanPeriod.

Compute the monthly and totalpayments.

Output the results.


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Fig. 3.13

The object diagram for the programLoanCalculator.


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Steps of implementation:1. Start with code to accept three input

values.

2. Add code to output the results.

3. Add code to compute the monthlyand total payments.

4. Update or modify code and tie up

any loose ends.


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Step 1 Development: Input Three DataValues

Call the showInputDialog method to

accept three input values: loan amount,

annual interest rate,

loan period.


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/*

Chapter 3 Sample Development: Loan Calculator(Step 1)

File: Step1/Ch3LoanCalculator.java

Step 1: Input Data Values

*/


class Ch3LoanCalculator {

public static void main (String[] args) {

double loanAmount,annualInterestRate;

int loanPeriod;

String inputStr;


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//get input values

inputStr = JOptionPane.showInputDialog(null,"Loan Amount (Dollars+Cents):");

loanAmount = Double.parseDouble(inputStr);

inputStr = JOptionPane.showInputDialog(null,

"Annual Interest Rate (e.g.,9.5):");

annualInterestRate = Double.parseDouble(inputStr);


"Loan Period - # of years:");

loanPeriod = Integer.parseInt(inputStr);


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//echo print the input values

System.out.println("Loan Amount: $" +loanAmount);

System.out.println("Annual Interest Rate: " +annualInterestRate + "%");

System.out.println("Loan Period (years): " +loanPeriod);

}

}


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Step 2 Development: Output Values

We must determine an appropriate

format to display the computed results,

so that the results will becomprehensible to the user.


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Fig. 3.14

Two display formats: One with inputvalues displayed, and the other with

only the computed values displayed.


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/*

Chapte

r3 S

ample De

velopment: Lo

an C

alcula

tor(Step2)


Step2: Display the Result

*/




double loanAmount,

annu

alInte

restR

ate;

double monthlyPayment,

totalPayment;

int loanPeriod;

String inputStr;


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//get input values

inputStr = JOptionPane.showInputDialog(null,"Loan Amount (Dollars+Cents):");



"Annual

Interest R

ate (e.g.,9.5):");


inputStr = JOptionPane.showInputDialog(null,"Loan Period - # of years:");



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//compute the monthlyand totalpayments

monthlyPayment = 132.15;totalPayment = 15858.10;

//display theresult


System.out.

print

l

n("Annual

Interes

t Ra

te: " +annualInterestRate + "%");


System.out.println("\n");//skip two lines

System.out.println("Monthlypayment is $ " +monthlyPayment);

System.out.println(" TOTAL payment is $ " +totalPayment);

}

}


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Step 3 Development: Compute LoanAmount

Complete the program by implementing

the formula derived in the design

phase.

We must convert the annual interest

rate (input value) to a monthly interest

rate (per the formula), and the loanperiod to the number of monthly

payments.


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/*

Chapte

r3 S

ample De

velopment: Lo

an C

alcula

tor

(Step 3)


Step 3: Compute the monthlyand totalpayments

*/




final int MONTHS_IN_YEAR = 12;

double loanAmount,annualInterestRate,monthlyPayment, totalPayment;

double monthlyInterestRate;

int loanPeriod,numberOfPayments;

String inputStr;


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//get input values

inputStr = JOptionPane.showInputDialog(null,"Loan Amount(Dollars+Cents):");


inputStr = JOptionPane.showInputDialog(null,"Annual Interest Rate (e.g.,9.5):");

annualInterestRate=Double.parseDouble(inputStr);

inputStr = JOptionPane.showInputDialog(null,"Loan Period - # of years:");



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monthlyInterestRate = annualInterestRate/MONTHS_IN_YEAR / 100;

numberOfPayments = loanPeriod * MONTHS_IN_YEAR;

monthlyPayment =

(loanAmount * monthlyInterestRate) /

(1 - Math.pow(1/(1 + monthlyInterestRate),numberOfPayments ) );

totalPayment = monthlyPayment * numberOfPayments;


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//display theresult


System.out.println("Annual Interest Rate: " +annualInterestRate + "%");



System.out.println("Monthlypayment is $ "

+ monthlyPayment);

System.out.println(" TOTAL payment is $ "

+ totalPayment);

}

}


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Step 4 Development: Finishing Up

Finalize the program by making

necessary modifications or additions.

We will add a program description and

format the monthly and total payments

to two decimal places.


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/*

Chapter 3 Sample Development: Loan Calculator (Step 4)


Step 4: Finalize theprogram

*/


import java.text.*;



final int MONTHS_IN_YEAR = 12;

double loanAmount,annualInterestRate;

d

ouble

monthlyPayment,tot

al

Payment;

double monthlyInterestRate;

int loanPeriod, numberOfPayments;

String inputStr;

DecimalFormatdf = new Decim

alFormat("0.00");


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//describe theprogram

System.out.println("Thisprogram computes themonthlyand total");

System.out.println("payments fora given loanamount,annual ");

System.out.println("interest rate,andloan

period.");

System.out.println("Loan amount in dollarsandcents,e.g., 12345.50");

System.out.println("Annual interest rate inper

centa

ge,e.g.

,12.75")

;

System.out.println("Loan period in number ofyears,e.g., 15");



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//get input values

inputStr = JOptionPane.showInputDialog(null,"Loan Amount(Dollars+Cents):");



"Annual

Interest R

a

te (e.g.,9.5):");



"Loan Period - # of years:");



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monthlyInterestRate = annualInterestRate/MONTHS_IN_YEAR / 100;

numberOfPayments = loanPeriod * MONTHS_IN_YEAR;

monthlyPayment =

(loanAmount * monthlyInterestRate) /

(1 - Math.pow(1/(1 + monthlyInterestRate),numberOfPayments ) );

totalPayment = monthlyPayment * numberOfPayments;


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