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 byteshort int longfloatdouble 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 typesStorage RequiredRange of Values byte8 bits (byte)-128 to +127 Short16 bits (2 bytes)-32,768 to +32,767 int32 bits (4 bytes02,147,483,648 to +2,147,483,647 long64 bits (8bytes)-9223,372,036,854,775,808 to +9223,372,036,854,775,807

Floating Point Type Data TypeStorage requiredRange of Values float32 bits (4 bytes)-3.4 x to +3.4 x double64 bits (8 bytes)-1.7 x to +1.7 x

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_ C:\chapter3\unicodeChar.java:5: possible loss of precision found : doublerequired: int int x = 2.0; ^ 1 error Process completed

Assignment Incompatibility Consider the following statement: short x = ; This gives rise to syntax error also. Configuration: j2sdk1.4.1_ C: \chapter3\unicodeChar.java:5: possible loss of precision found : int required: short short x = ; ^ 1 error Process completed

Assignment Incompatibility Consider the following segment of code: int x = 2; byte y = x; -----Configuration: j2sdk1.4.1_ C:\istings\data_types\default_types.java:6: possible loss of precision found : int required: 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 typeStorage RequiredRange in DecimalRange in Unicode Char16 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_ C: \chapter3\unicodeChar.java:5: incompatible types found : int required: boolean boolean x = 0; ^ 1 error Process 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 OperatorNameAlgebraic formExampleResult +Additionx + y Subtractionx – y *Multiplicationx * y18 * 236 /Divisionx / y37 / 57 %Modulus operationx % y37 % 52

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.

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 Packing 2.{ 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; packing(int books) 12.{ 13.this.books = books; 14.}

Class PackingBooks – Mutator Method void determineBoxes() 17.{ 18.big = books/XTRA_LARGE_BOX; 19.books = books % XTRA_LARGE_BOX; large = books/LARGE_BOX; 22.books = books % LARGE_BOX; medium = books/MEDIUM_BOX; 25.small = books % MEDIUM_BOX; 26.}

Class PackingBooks – Mutator Method 27. int getBigBox() 28.{ 29.return big; 30.} int getLargeBox() 33.{ 34.return large; 35.} int getMediumBox() 38.{ 39.return medium; 40.} 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