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Lesson 02

Data Types and Statements

MIT 11053, Fundamentals of Programming

By: S. Sabraz Nawaz

Senior Lecturer in MIT

Department of MIT

FMC, SEUSL

Exercise

• A university pays its Academic Staff

oAcademic Allowance 39% of Basic Salary

o Research Allowance 45% of Basic Salary

o Cost of Living Allowance 7,550/=.

• And deducts UPF 8% of the Basic Salary.

• Write a Java program to input the Basic Salary.

Calculate the above and display them all with

Net Salary

Fundamentals of Programming by

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Topics Covered

• Statements

• Variables

• Data Types

• Arithmetic Calculations

• Pre and Post increment operators

• Taking Input from User


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Statements

• A Statement is the simplest task you can accomplish in Java.


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int othrs=5;

System.out.println("netsalary= "+netsal);

You need to put a semi colon ; at theend of a statement.

Variables

• Variables are locations in memory where values can be

stored


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Variable Name

• Variable is a location in memory

• Each location in memory has a memory address, which is a number

o This long number is inconvenient to use when we want to access the memory location

• We give a human understandable name to refer to this number

o e.g. age, quantity

• The compiler and the interpreter maps this name to the memory address number


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Value of a Variable

• At a given time one value can be stored under the variable


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quantity

Variable Type

• You need to specify what type of data is to be stored. e.g.

int, char

• This is because we must instruct how much memory

should be reserved by the program to store the value of a

variable

• The amount of memory needed depends on the maximum

of the value we need to store in the variable.


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Variable Type…


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Java Data Types

• Java supports eight primitive data types.

• These are built into the language itself.

• Consists of Numeric Types, char type and Boolean type.

• Remember String is not a primitive data type in Java

o String is a class in Java, thus it is handled as a data type derived from a class.

• In Java we write classes and class can be a data type

o Eg: If you write a class called Student you can use it as the Student

data type


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Data Types


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Name Range Storage Size

byte –2

7 (-128) to 2

7–1 (127) 8-bit signed

short –2

15 (-32768) to 2

15–1 (32767) 16-bit signed

int –2

31 (-2147483648) to 2

31–1 (2147483647) 32-bit signed

long –2

63 to 2

63–1 64-bit signed

(i.e., -9223372036854775808

to 9223372036854775807)

float Negative range: 32-bit IEEE 754

-3.4028235E+38 to -1.4E-45

Positive range:

1.4E-45 to 3.4028235E+38

double Negative range: 64-bit IEEE 754

-1.7976931348623157E+308 to

-4.9E-324

Positive range:

4.9E-324 to 1.7976931348623157E+308

Declaring Variables

int x; // Declare x to be an

// integer variable;

double radius; // Declare radius to

// be a double variable;

char a; // Declare a to be a

// character variable;


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Declaring Variables


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public static void main (String args[]) {int count;String title;boolean isAsleep;...

}

Variables are usually defined at thebeginning. However this need not always

be the case.

Declaring Variables


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int x, y, z;

String firstName, lastName;

Multiple variables can be defined under one type

Declaring Variables

• Once declared the variable need to be initializedo Initialization – Specify the value we want to store in the variable


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int myAge;

myAge = 32;

String myName = “SaNa";

boolean isTired = true;

int a = 4, b = 5, c = 6;

You can also initialize variables asthe declaration is done.

Declaring and Initializing

in One Step

• int x = 1;

• double d = 1.4;


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int age=19;

The above statements are identical

int age;

…

age = 19;

Variable Names


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int age;

float $money;

char my_char;

long _no;

String name7;

A Variable Name should start with an Alphabetical letter or $, or _ symbol

The other characters can include numbersBut you cannot use symbols like @, #, etc

Variable Names


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int my age;

float @money;

char 6my_char;

long no*;

The above names are incorrect.You cannot have spaces and other

special symbols.

Variable Names


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int qty;

String firstName;

float basicSal, netSal;

It’s best if you can give suitable (short but meaningful) variable names.

Numeric Operators


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Name Meaning Example Result

+ Addition 34 + 1 35

- Subtraction 34.0 – 0.1 33.9

* Multiplication 300 * 30 9000

/ Division 1.0 / 2.0 0.5

% Remainder 20 % 3 2

Arithmetic Expressions


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)94

(9))(5(10

5

43

y

x

xx

cbayx

is translated to

(3+4*x)/5 – 10*(y-5)*(a+b+c)/x + 9*(4/x + (9+x)/y)

How to Evaluate an Expression


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• Though Java has its own way to evaluate an expression behind the

scene, the result of a Java expression and its corresponding

arithmetic expression are the same. Therefore, you can safely apply

the arithmetic rule for evaluating a Java expression.

3 + 4 * 4 + 5 * (4 + 3) - 1

3 + 4 * 4 + 5 * 7 – 1

3 + 16 + 5 * 7 – 1

3 + 16 + 35 – 1

19 + 35 – 1

54 - 1

53

(1) inside parentheses first

(2) multiplication

(3) multiplication

(4) addition

(6) subtraction

(5) addition

Shortcut Assignment Operators


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Operator Example Equivalent

+= i += 8 i = i + 8

-= f -= 8.0 f = f - 8.0

*= i *= 8 i = i * 8

/= i /= 8 i = i / 8

%= i %= 8 i = i % 8

Numeric Type Conversion

Consider the following statements:

byte i = 100;

long k = i * 3 + 4;

double d = i * 3.1 + k / 2;


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Conversion Rules

When performing a binary operation involving two operands

of different types, Java automatically converts the operand

based on the following rules:

1. If one of the operands is double, the other is converted into

double.

2. Otherwise, if one of the operands is float, the other is converted

into float.

3. Otherwise, if one of the operands is long, the other is converted

into long.

4. Otherwise, both operands are converted into int.


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Type Casting

Implicit casting

double d = 3; (type widening)

Explicit casting

int i = (int)3.0; (type narrowing)

int i = (int)3.9; (Fraction part is truncated)


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byte, short, int, long, float, double

range increases

The String Type

The char type only represents one character. To represent a string

of characters, use the data type called String. For example,

String message = "Welcome to Java";

String is actually a predefined class in the Java library just like the

System class. The String type is not a primitive type. It is known

as a reference type. Any Java class can be used as a reference type

for a variable.


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String Concatenation

// Three strings are concatenated

String message = "Welcome " + "to " + "Java";

// String Chapter is concatenated with number 2

String s = "Chapter" + 2; // s becomes Chapter2

// String Supplement is concatenated with character B

String s1 = "Supplement" + 'B'; // s1 becomes SupplementB


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Exercises

1. Write a Java program that takes three marks of an exam and displays the

total and the average.

2. Write a program to input how many notes, coins of denominations of

1000/=, 500/=, 200/=, 100/= 50/=,20/=,10/=,5/=, 2/= and 1/= are

available. Print the total amount


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Taking User Inputs


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Using Scanner Class

• The Scanner class is a class in java.util, which allows the user

to read values of various types.

• The Scanner looks for tokens in the input. A token is a series of

characters that ends with what Java calls whitespace. A

whitespace character can be a blank, a tab character, a carriage

return, or the end of the file.


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Using Scanner Class


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Method Returns

int nextInt() Returns the next token as an int.

long nextLong() Returns the next token as a long.

float nextFloat() Returns the next token as a float.

double nextDouble()

Returns the next token as a double.

String next()Finds and returns the next complete token from this scanner andreturns it as a string; a token is usually ended by whitespace such asa blank or line break.

String nextLine() Returns the rest of the current line, excluding any line separator atthe end.

Using Scanner Class


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01

02

03

Using Scanner Class…


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Solution for Restaurant Bill – Exam - Answer


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Solution for Restaurant Bill – Classroom Exam


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End of Lecture


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