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Example program• //This will convert a numeric grade into a letter grade• import TerminalIO.KeyboardReader;
• public class Grades• {• public static void main (String args [])• {• //Variables• double grade1,grade2, grade3, total;• //End of Variables•• //Input• KeyboardReader reader = new KeyboardReader();• System.out.print ("Please enter in the first grade: ");• grade1 = reader.readDouble();• System.out.print ("Please enter in the second grade: ");• grade2 = reader.readDouble();• System.out.print ("Please enter in the third grade: ");• grade3 = reader.readDouble();• //End of Input•• //Calculations• total = (grade1 + grade2 + grade3) / 3.0;• System.out.println ("The average is: "+total);• //End of Calculations•• //If Statements• if (total >= 94)• System.out.println ("The letter grade is: A");• if (total >= 84 && total <94)• System.out.println ("The letter grade is: B");• if (total >= 76 && total <84)• System.out.println ("The letter grade is: C");• if (total >= 68 && total <76)• System.out.println ("The letter grade is: D");• if (total <68)• System.out.println ("The letter grade is: F");• }• }
Compound Assignment OperationsSimple AssignmentCompound AdditionCompound
SubtractionCompound
MultiplicationCompound DivisionCompound Remainder
=+=-=*=/=%=
(integers only)
Compound Assignment Equalities
x = x + 10x = x – 10x = x * 10x = x / 10x = x % 10
x += 10x –= 10x *= 10x /= 10x %= 10
Compound Assignments
Translate the following statements to equivalent statements that use extended assignment operators:
a. X *=2 a. X = X *2;
b. Y = Y % 2; b. Y %= 2
Math Class
• The math class is quite extensive but we will concentrate a just a few of it’s properties:
static int abs(int x) Returns the absolute value of an integer x
static double abs (double x) Returns the absolute value of a double x
static double pow(double base, double exponent)
Returns the base raised to the exponent.
static long round (double x) Returns x rounded to the nearest whole number.
static int max (int a , int b) Returns the greater of a and b
static int min(int a , int b) Returns the lesser of a and b
static double sqrt (double x) Returns the square root of x.
Examples of Math Class Methods
int m;double x;
m = Math.abs(-7) // m equals 7x = Math.abs(-7.5) // x equals 7.5x = Math.pow(3.0,2.0) // x equals 3.0^2.0 = 9.0x = Math.pow(16.0, .25) // x equals 16.0 ^ .25 =
2.0m = Math.max(20,40) // m equals 40m = Math.min(20,40) // m equals 20m = (int) Math.round(4.27) // m equals 4
Math Class
//Given the area of a circle, compute its radius.
double area = 10.0, radius;radius = Math.sqrt(area / Math.PI);
Math.PI is accurate to about 17 decimal places
Random Class
• The Random class has two methods that will generate a random integer or double.
Method What is Doesint nextInt(int n) Returns a integer chosen at
random from among 0,1,2,3,…,n-1
double nextDouble() Returns a double chosen at random between 0.0 and 1.0, inclusive.
Example of Random Class Methods
Import java.util.Random;
Random generator = new Random();int i;double j;
i = generator.nextInt(3); // would give a // random number 0,1, or 2.
j = generator.nextDouble(); // would give a // random number // between 0 and 1
Control Structures
• A control structure is simply a pattern for controlling the flow of a program module.
• The three fundamental control structures of a structured programming language are sequence, selection, and iteration.
• Sequence control structure is what you have been doing up until now. The second two is what we are going to take a look at next.
Selection/Iteration Structure
• Selection and Iteration allow the flow of the program to be altered, depending on one or more conditions.
• Selection is implemented by using a if, if/else, and switch statements.
• Iteration is implemented by using the while, do/while, and for statements.
The IF statement
• The if statement works much the same as a if/then statement in Visual Basic.
• It uses relational operators to test if something is true or false.
• If it is true, the program will execute the statement(s) within the if statement.
• If it is false, the program will bypass the statements and continue with the statements following the if statement.
Syntax of the If Statement
if (test expression)
{
statement1;
statement2;
statementn;
}
//this is an example of a compound statement
IF/ELSE Statement
• The IF/ELSE statement works in the same manner as the if/then/else in Visual Basic.
• It is considered a double-alternative statement.
• If the expression evaluates as true, then the statements inside the if are executed.
• If the expression evaluates as false, then the statements inside the else are executed.
Syntax for if/else
if (test expression){
statement1;statement2;statementn;
}else{
statement1;statement2;statementn;
}//example of compound statements
Relational Operators
Relational operators allow two quantities to be compared.
= = Equal to
! = Not equal to
< Less than
< = Less than or equal
> Greater than
> = Greater than or equal
Switch Statement
• The switch statement works in the same manner as the case select statement in Visual Basic.
• A selector variable is first evaluated to produce a value.
• The selector is then compared to a series of cases.
• If the selector value matches one of the case values, the corresponding case statements are executed.
Syntax for a Switch Statement
switch (selector variable) //must be int or char{
case case1value : case1statements;break;
case case2value : case2statements;break;
case casenvalue : case_N_statements;break;
default : case exception statements;
}