meljun cortes java numerical data types and expressions

8/13/2019 MELJUN CORTES Java Numerical Data Types and Expressions

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MELJUN CORTES MBA MPA BSCS ACS

Chapter 3-

JAVA Numerical Expression

Numerical

Data

MELJUN CORTES


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MELJUN CORTES


Chapter 3 Objectives

After you have read and studied this

chapter, 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.


chapter, you should be able to

Write mathematical expressions, using

methods in the Mathclass.

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.


chapter, 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.inand outputdata using System.out.


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3.1 Variables

To compute the sum and the differenceof xand yin 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 as

int x, y;

is made, memory locations to store datavalues for xand yare allocated.

These memory locations are calledvariables, and xand yare 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 memory

location.



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.



3.1 Variables

There are six numerical data types in

Java: byte

short

int

long

float

double

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

Floatand doubleare for real numbers.



3.1 Variables

At the time a variable is declared, it can

also be initialized.

int count = 10, height = 34;

We assign a value to a variable byusing an assignment statement.

Do not confuse mathematical equalityand assignment. The following is not

valid Java code:

4 + 5 = x;



3.1 Variables

The only difference between a variable

for 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.



Fig. 3.1

A diagram showing how two memory

locations (variables) are declared, and

values are assigned to them.



Fig. 3.2

A difference between object declaration

and numerical data declaration.



3.1 Variables

We use the newcommand to create an

object.

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.



Fig. 3.3

An effect of assigning the content of one

variable to another.



3.2 Arithmetic Expressions

Arithmetic operators in Java


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An illustration of a subexpression in the

expression x + 3 * y


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Precedence rules for arithmetic

operators 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, we

use 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 decimal

point, it is of type doubleby 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 as

Number 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 classesare used to perform

necessary type conversions, such asconverting a String object to a

numerical value.


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/*

Chapter 3 Sample Program: Compute Area andCircumference

File: Ch3Circle.java

*/

import javax.swing.*;

import java.text.*;

class Ch3Circle {

public static void main( String [] args ) {

final double PI = 3.14159;

String radiusStr;


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double radius, area, circumference;

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

radius = Double.parseDouble(radiusStr);

//compute area and circumference

area = 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 compiler

interprets 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 input

value 2.35 was entered into theCh3Circle program.


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Fig. 3.5

The result of formatting the output

values by using a DecimalFormatobject.


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3.5 Standard Output

The showMessageDialogmethod is

intended for displaying short one-linemessages, 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 for

displaying multiple lines of text.


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3.5 Standard Output

We use the printmethod to output a

value.

The printmethod will continue printing

from the end of the currently displayedoutput.


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Fig. 3.7

Result of executing

System.out.print(Hello, Dr.Caffeine.).


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Fig. 3.8

Result of sending five printmessages

to System.outof Figure 3.7.


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3.5 Standard Output

The printmethod will do the necessary

type conversion if we pass numericaldata.

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

will start on the next line by using

printlninstead of print.


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Fig. 3.9

The result of mixing printwith four

printlnmessages to System.out.


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3.6 Standard Input

The technique of using System.into

input data is called standard input.

We can only input a single byte usingSystem.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 one

integer 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 MathClass

The Mathclass in thejava.lang

package contains class methods forcommonly used mathematical

functions.

Table 3.6 contains a partial list of class

methods available in the Mathclass.


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3.8 The GregorianCalendarClass

The GregorianCalendarclass is useful

in manipulating calendar informationsuch 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 Ch3TestCalendar

program at November 11, 2002, 6:13p.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 program

LoanCalculator.


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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 Data

Values

Call the showInputDialogmethod 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);


"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 input

values displayed, and the other withonly the computed values displayed.


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/*

Chapter 3 Sample Development: Loan Calculator

(Step 2)


Step 2: Display the Result

*/




double loanAmount,

annualInterestRate;

double monthlyPayment,

totalPayment;

int loanPeriod;

String inputStr;


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//get input values


"Loan Amount (Dollars+Cents):");



"Annual Interest Rate (e.g.,

9.5):");






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//compute the monthly and total payments

monthlyPayment = 132.15;

totalPayment = 15858.10;

//display the result

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


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

loanPeriod);

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

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

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

}

}


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Step 3 Development: Compute Loan

Amount

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.

S C


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/*

Chapter 3 Sample Development: Loan Calculator (Step 3)


Step 3: Compute the monthly and total payments

*/




final int MONTHS_IN_YEAR = 12;

double loanAmount, annualInterestRate,monthlyPayment, totalPayment;

double monthlyInterestRate;

int loanPeriod, numberOfPayments;

String inputStr;

3 9 S l D l L C l l


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//get input values


"Loan Amount(Dollars+Cents):");loanAmount = Double.parseDouble(inputStr);


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

annualInterestRate=Double.parseDouble(inputStr);

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


3 9 S l D l t L C l l t


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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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System.out.println("Loan Amount: $" +

loanAmount);



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

loanPeriod);


System.out.println("Monthly payment 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 the program

*/


import java.text.*;



final int MONTHS_IN_YEAR = 12;

double loanAmount, annualInterestRate;

double monthlyPayment, totalPayment;

double monthlyInterestRate;

int loanPeriod, numberOfPayments;

String inputStr;

DecimalFormat df = new DecimalFormat("0.00");



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//describe the program

System.out.println("This program computes the

monthly and total");

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

System.out.println("interest rate, and loan

period.");

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

System.out.println("Annual interest rate inpercentage, e.g., 12.75");

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




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//get input values


"Loan Amount(Dollars+Cents):");



"Annual Interest Rate (e.g.,

9.5):");







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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;

3 9 Sample De elopment Loan Calc lator


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System.out.println("Loan Amount: $" +

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


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


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

+ df.format(monthlyPayment));

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

+ df.format(totalPayment));

}

}

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