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Data Types and Operations On Data

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

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Data Types and Operations On Data

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  1. 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

  2. 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

  3. 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

  4. 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.

  5. Introduction – Data Types • In the first section we: • Study the fundamental data types in Java, and • how they relate to programming. • 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: • The String class • The Math class • The wrapper classes

  6. 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: • Primitive, and • Reference type • Primitive types are atomic • They cannot be decomposed into simpler types • Reference types are constructed from: • Primitive types, • As well as from other reference types

  7. Data Types Data types Primitive types Reference types Floating Point Boolean types Java classes Integral types User defined classes Integers Character int byte short long char float double boolean

  8. 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

  9. Integer Type

  10. Floating Point Type

  11. Storage Space byte short int long

  12. Default Values • Integer types – 0 • Floating point types – 0.0

  13. 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: int int x = 2.0; ^ 1 error Process completed

  14. 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: short short x = 150000; ^ 1 error Process completed

  15. 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 precision • found : int • required: byte • byte y = x; • ^ • 1 error • Process completed.

  16. 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’

  17. 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 types found : int required: boolean boolean x = 0; ^ 1 error Process completed.

  18. 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

  19. 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

  20. 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.

  21. 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.

  22. 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.

  23. 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

  24. PackingBooks - Attributes • Constants • Extra large box • Large box • Medium box • Small box • Variables • books • Extra large • Large • Medium • Small

  25. PackingBooks - Constructor • The problem suggests only one argument required – the number of books • PackingBooks( books) Accessor Methods getBigBox() getLargeBox() getMediumBox() getSmallBox() Mutator Method determineBoxes()

  26. Class PackingBooks • class Packing • { • static final int XTRA_LARGE_BOX = 25, • LARGE_BOX = 15, • MEDIUM_BOX = 5, • SMALL_BOX = 1; • int books; • int big, large, medium, small; • Packing(int books) • { • this.books = books; • }

  27. Class PackingBooks – Mutator Method • void determineBoxes() • { • big = books/XTRA_LARGE_BOX; • books = books % XTRA_LARGE_BOX; • large = books/LARGE_BOX; • books = books % LARGE_BOX; • medium = books/MEDIUM_BOX; • small = books % MEDIUM_BOX; • }

  28. Class PackingBooks – Mutator Method • int getXtraLargeBox() • { • return big; • } • int getLargeBox() • { • return large; • } • int getMediumBox() • { • return medium; • } • int getSmallBox() • { • return small; • } • }

  29. Class PackingBooks – Test class • class TestPacking • { • public static void main(String [] arg) • { • Packing pack = new Packing(127); • pack.calculate(); • System.out.println(pack.getXLarge() + " extra large boxex\n" + pack.getLarge() • + " large boxex\n" + pack.getMedium() • + " medium boxes\n" + pack.getSmall() • + " small box\n" + pack.getTotal() • + " total boxes\n") ; • } • }

  30. Integer Operations Integer operations can produce erroneous results

  31. Floating Point Operations Floating -Point operations can produce erroneous results

  32. Evaluate Arithmetic expressions • In general, arithmetic expressions are evaluated from left to right 2 + 3 – 4 + 5 2 + 3 – 4 + 5 5 1 6

  33. Evaluate Arithmetic expressions • The order of evaluating an expression may be altered. • Criteria • Unary operators are done first - they have the highest priority. • Parenthesize (sub-expressions) have the next level of priority. • Multiplication, division and modulus have next level of priority • Addition and subtraction have the lowest level of priority.

  34. Evaluate Arithmetic expressions The operations * / % must be carried out before addition and subtraction 2 + 3 – 4 * 5 2 + 3 – 4 * 5 20 5 -15

  35. Evaluate Arithmetic expressions The parentheses must be carried out before + - * / % 2 + ( 3 – 4) * 5 2 + ( 3 – 4 ) * 5 -1 -5 -3

  36. Evaluate Arithmetic expressions 11 % 4 * 2 – 14/3 + (8 –2 * -3) 11 % 4 * 2 – 14 / 3 + ( 8 – 2 * -3 ) -6 14 3 6 4 2 16

  37. Converting Algebraic Expression s = s0 +v0t + ½ gt2 • s = s0 + v0 * t + g * t * t / 2.0; or • s = s0 + v0 * t +1.0/2 *g * t * t ; or • s = s0 + v0 * t +0.5 *g * t * t ; or • s = s0 + v0 * t + (float)1/2 *g * t * t ;

  38. Centigrade = • class DataTypes • { • public static void main(String[] arg) • { • double fahrenheit = 42.0; • double centigrade = 5/9*(fahrenheit - 32.0); • System.out.println(centigrade); • } • }

  39. The Fundamental Types What will happen if you attempt to compile each of the following lines of code? • int x = 25.0; • float x = 1.0; • byte x = 130; • char x = 128; • boolean x = 1;

  40. Relational Operator and Operations • There are six binary relational operators in Java. • They are used to form conditional expressions. • They are used with primitive numeric and the character types only.

  41. Relational Operators & Operations

  42. Relational expression • Relational expression is a combination of two primitive types separated by a relational operator. • The result from evaluating the expression is one of the boolean values,trueorfalse. • The general form of simple conditional statements is: • Left_Operand Relational_Operator Right_Operand Example: • 10 > 15 • ‘a’ != ‘A’

  43. Evaluating Relational Expressions • When evaluation relational expressions, you must: • First resolve all arithmetic expressions to get the primitive values. • Then compare the primitive values as specified by the relational operator Example: Use the following declaration to evaluate the relational expressions int x = 10, y = 20; double z = 5.0; Evaluate the following relational expressions. • x / y < z • x%y - 10 >= x - y/x - z

  44. Evaluate Relational Expression: x / y < z int x = 10, y = 20; double z = 5.0; x / y < z 0 true

  45. Evaluate Relational Expression: x%y - 10 >= x - y/x - z int x = 10, y = 20; double z = 5.0; x % y - 10>= x - y / x - z 10 2 0 8 3.0 false

  46. Evaluate Relational Expression: x%y – (10 >= x ) - y/x - z int x = 10, y = 20; double z = 5.0; X % y – ( 10 >= x ) - y/x - z

  47. Evaluate Relational Expression: x%y – (10 >= x ) - y/x - z int x = 10, y = 20; double z = 5.0; x % y - ( 10 >= x ) - y / x - z 10 true ????

  48. Evaluating Relational Expressions • The value from a relational expression can be assigned to a Boolean variable. The format is: boolean id = relational_expression. For example : int x = 120; double y = 20; boolean flag = 2 * x > y + 2; • Note: • The relational expression must be evaluated first. • The resulting value is assigned to the Boolean variable flag. • In this case the value true is assigned to the variable flag.

  49. Logical Operator and Operations • Java has three logical operators: • logical-AND ( && ) – Determines the validity of two relational expressions • logical-OR ( || ) - Determines the validity of one or both two relational expressions • logical-NOT ( ! ) – Negates the result of a boolean value • This means that the relational expressions must first be evaluated, before logical operators can be applied.

  50. Evaluate Logical Expression: x + y > z && x – y < z int x = 10, y = 20; double z = 5.0; x + y > z && x – y < z 30 -10 truetrue true

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