Data Types and Operations On Data
Objective
• To understand what data types are
• The need to study data types
• To differentiate between primitive types and reference types
• To know the data range and storage requirements for each type
• To know the conditions for data conversion
• To know the permissible operations that can be performed on data
• To be able to evaluate expressions
Data Types and Operations On Data
• Introduction• Data Types • Primitive Type
Integral Type Floating Point Type Character Type Boolean Type
• Type Compatibility• Reference Type• Arithmetic Operator and Operations• Arithmetic Expressions• Relational Operator and Operations• Relational Expressions• Logical Operator and Operations• Input and Output Operations
Data Types - Introduction
• The concept of data type is like what the bolts and nuts are to a piece of
machinery.
• It is impossible to write meaningful program, without understanding:
Data types, data values
The amount of memory required for each type of data, and
The permissible operations that can be performed on data
Data Types - Introduction
• Like anything else, conservation of the use of memory is important.
• Some former languages did not consider conserving memory.
• Most of them had only two ways to store numeric values:
int, for integers, and
float, for floating point values.
• Hence wasting memory, especially when storing small values ;
• The amount of memory for each value, large or small, is the same.
Introduction – Data Types
• In the first section we:
a) Study the fundamental data types in Java, and
b) how they relate to programming.
c) Focus on the operations that can be performed on each type.
• The second section introduces the reference type.
• This includes some of the fundamental Java classes, such as:
a) The String class
b) The Math class
c) The wrapper classes
The Fundamental Types
• We had established that data is vital to a program.
• It must be stored in primary memory for the processor to handle it.
• The Java specifies two broad categories of data types:
a) Primitive, and
b) Reference type
• Primitive types are atomic
• They cannot be decomposed into simpler types
• Reference types are constructed from:
a) Primitive types,
b) As well as from other reference types
Data Types
Data types
Primitive types Reference types
Integral types Floating Point
boolean
Integers
byte shortint long float double
User defined classes
Java classes
char
Boolean types
Character
Primitive Types
• Primitive types are atomic
• There are three types – integral, floating point, and boolean
• Integral – they can be represented by an integer value
• There are two groups – integer and character
• Integer – byte, short, int, long
Integer Type
Data types Storage Required Range of Values
byte 8 bits (byte) -128 to +127
Short 16 bits (2 bytes) -32,768 to +32,767
int 32 bits (4 bytes0 2,147,483,648 to +2,147,483,647
long 64 bits (8bytes) -9223,372,036,854,775,808 to
+9223,372,036,854,775,807
Floating Point Type
Data Type Storage required Range of Values
float 32 bits (4 bytes) -3.4 x 1038 to +3.4 x 1038
double 64 bits (8 bytes) -1.7 x 10308 to +1.7 x 10308
Storage Space
long
int
short
byte
Default Values
• Integer types – 0
• Floating point types – 0.0
Assignment Incompatibility
• Variables can be initialized wrongly
• This situation gives rise to syntax errors
• Consider the following statement:
int x = 2.0;
Configuration: j2sdk1.4.1_02 <Default>----C:\chapter3\unicodeChar.java:5: possible loss of precision found : double required: intint x = 2.0; ^1 errorProcess completed
Assignment Incompatibility
• Consider the following statement:
short x = 150000;
• This gives rise to syntax error also.
Configuration: j2sdk1.4.1_02 <Default>----C: \chapter3\unicodeChar.java:5: possible loss of precision found : int required: shortshort x = 150000; ^1 errorProcess completed
Assignment Incompatibility
Consider the following segment of code:
int x = 2;
byte y = x;
-----Configuration: j2sdk1.4.1_02 <Default>----C:\istings\data_types\default_types.java:6: possible loss of precisionfound : intrequired: byte byte y = x; ^1 error
Process completed.
Character type - char
• The character data type named char is :
Any printable symbol found on the keyboard, or
Certain sequence of characters called escape sequence. • In either case, it requires 16 bits (2 bytes) of memory to store the char value
• A char value can be represented decimal value in the range 0 to 65,536, or as Unicode character in the range ‘\u0000” to ‘\uFFFF’
Data type Storage Required Range in Decimal Range in Unicode
Char 16 bits (2 bytes) 0 to 65,536 \u0000 to \uFFFF
Boolean Type
• Java’s logical data type is called boolean.
• The set of values that represent the boolean data type is true and false.
• This data type is implemented when comparing primitive types. • Boolean variables are declared the same way as other variables
• The default of a boolean variable is false • Consider the following statement
boolean x = 0;
Configuration: j2sdk1.4.1_02 <Default>----C: \chapter3\unicodeChar.java:5: incompatible typesfound : int required: boolean boolean x = 0; ^1 errorProcess completed.
Operator and Operations on Data
• Computers are known as number crunching machines.
• To crunch numbers, they need to perform operations on the numbers
• Java has five types of operations to perform on primitive data values:
Arithmetic operations
Relational operations
Logical operations
Bit-wise operations, and
Bit-shift operations
• We will study the first three – Arithmetic, Relational and Logical operations
Arithmetic Operator and Operations
• Java defines five binary arithmetic operators: + - * / %• They are used to form arithmetic expressions. • The format of an arithmetic expression is:
operand operator operand;
• Operands are any valid identifier or numeric literal, and • Operator is any of five arithmetic operators. See summarized below
Operator Name Algebraic form Example Result
+ Addition x + y 25 + 15 40
- Subtraction x – y 25 -1 15 10
* Multiplication x * y 18 * 2 36
/ Division x / y 37 / 5 7
% Modulus operation x % y 37 % 5 2
The operator / vs %
• The operators (+ , - , * ) have the usual arithmetic meaning
• The operator ( / ), gives the quotient when applied to division
That is why: 37/5 = 7 , and not 7.4
• The operator ( % ), gives the remainder when applied to division
Hence, 37 % 5 = 2.
2
___________
35
7375
2
___________
35
7375
The operator / vs %
• If a task takes a worker 127 minutes to complete, how many hours and how many minutes did it take the person to complete.
• If we were to program this, we would have to tell the computer precisely how to carry out the calculation. That is:
The number of hours would be (127 / 60) 2 hours, and
The number of minutes would be (127 % 60) 7 minutes.
Example
• A small company wants you to write a program to figure out the number of
boxes needed to ship book orders without wasting space. They have four types
of boxes: extra large, large, medium and small, which can hold 25, 15, 5 and 1
book(s) respectively.
• Write a Java program that accepts the number of books to be shipped and
displays the number of boxes needed with their type. For example if the
company wants to ship 81 books your output should be 3 big boxes, 1 medium
box and 1 small box.
Solution
• As before let us identify the elements of the problem
• Let us call the entity – PackingBooks
• No list the characteristics (attributes) of PackingBooks Constants Variables
• Constructor
• Operations Methods
PackingBooks - Attributes
• Constants Extra large box Large box Medium box Small box
• Variables books Extra large Large Medium Small
Class PackingBooks
1. class Packing2. {3. static final int XTRA_LARGE_BOX = 25,4. LARGE_BOX = 15,5. MEDIUM_BOX = 5,6. SMALL_BOX = 1;7.8. int books;9. int big, large, medium, small;10.11. packing(int books)12. {13. this.books = books;14. }
Class PackingBooks – Mutator Method
15.16. void determineBoxes()17. {18. big = books/XTRA_LARGE_BOX;19. books = books % XTRA_LARGE_BOX;20.21. large = books/LARGE_BOX;22. books = books % LARGE_BOX;23.24. medium = books/MEDIUM_BOX;25. small = books % MEDIUM_BOX;26. }
Class PackingBooks – Mutator Method
27. int getBigBox()28. {29. return big;30. }31.32. int getLargeBox()33. {34. return large;35. }36.37. int getMediumBox()38. {39. return medium;40. }41.42. int getSmallBox()43. {44. return small;45. }46. }
PackingBooks - Constructor
• The problem suggests only one argument required – the number of books
• PackingBooks( books)
Mutator Method
determineBoxes()
Accessor Methods
getBigBox()
getLargeBox()
getMediumBox()
getSmallBox()
PackingBooks
• XS