Tests - Coppin State University
SOME MATERIAL THAT COMPUTER SCIENCE STUDENTS MUST KNOW, C O L D
IMPORTS:
import java.io.*;
import java.util.Scanner;
DECLARATIONS:
final int MAXVAL = 100;
int x, n, numGrade, a, b, c, age, evenCount, oddCount, femaleCount, maleCount, i, sum;
int [ ] y = new int[MAXVAL];
char ch, gender, letGrade, sex, coffee, donuts;
double avg;
String str;
Scanner keyboard = new Scanner(System.in);
SETTING UP TO WORK WITH OUTPUT FILES
FileWrite fwriter = new FileWriter(“test.txt”); //associate fwriter with the actual file test.txt
OR
System.out.print(“What is the output filename? “);
str = keyboard.nextLine();
PrintWriter outputFile = new PrintWriter(str); //later, write to file associated with str
OR
File file = new File(str); //Note the File object
while(file.exists()) //If you don't want to overwrite an existing file
{
System.out.println("The file " + filename + " already exists.");
System.out.print(“What is the NEW output filename? “);
str = keyboard.nextLine();
file = new File(str);
}
PrintWriter outputFile = new PrintWriter(file); //An overloaded version of the PrintWriter constructor
OR
FileWriter fwriter = new FileWriter(str, true); //If you want to append (add) data to an existing file
PrintWriter outputFile = new PrintWriter(fwriter); //Another overloaded version of the PrintWriter constructor
SETTING UP TO WORK WITH INPUT FILES
File file = new File (“test.txt”); //associate file with the actual file test.txt
OR
System.out.print(“What is the input filename? “);
str = keyboard.nextLine();
File file = new File(str); //associate file with the file chosen by the user
while(!file.exists())
{
System.out.print("File " + str + " does not exist—filename? ");
str = keyboard.nextLine();
file = new File(str);
}
Scanner inputFile = new Scanner(file); //the actual reading is done with inputFile
TESTS (if statements):
positive, negative, zero, non-zero
if(x > 0) if(x < 0) if(x = = 0) if(x != 0)
above average, below, etc.
if(x > avg) if(x < avg)
even, odd
if(x % 2 == 0) if(x % 2 != 0)
evenCount++; oddCount++;
lower case, upper case, etc.
if(str.isLowerCase()) if(str.isUpperCase())
female, male
if(sex == ‘f ‘ || sex == ‘F’) if(sex.Character.toUpperCase() == ‘M’)
femaleCount++; maleCount++;
lowercase vowel
if(ch == ‘a’ || ch == ‘e’ || ch == ‘i’ || ch == ‘o’ || ch == ‘u’)
ladders
if(numGrade >= 90)
letGrade = ‘A’;
else if(numGrade >= 80)
letGrade = ‘B’;
else if(numGrade >= 70)
letGrade = ‘C’;
else if(numGrade >= 60)
letGrade = ‘D’;
else //if you fall through to here, it’s below 60—no need to ask
letGrade = ‘F’;
if x is between a and b
if(a ................
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