Cornelius Eanes's Programming Portal
[120] Programs that Write to Files
Goal: Find out how to write to a file.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Programs that Write to Files
/// File Name: Receipt.java
/// Date Finished: Mar 02, 2016
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
public class Receipt {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
PrintWriter fileOut;
double price = 2.791;
int numGallons;
try{
fileOut = new PrintWriter("receipt.txt");
} catch(IOException e) {
System.out.println("Sorry, I can't open the file 'receipt.txt' for editing.");
System.out.println("Maybe the file exists and is read-only?");
fileOut = null;
System.exit(1);
}
System.out.println("How many gallons of gas do you want?");
System.out.print("> ");
numGallons = input.nextInt();
System.out.println("Thanks for your purchase! Your receipt has been printed to \"receipt.txt\".");
fileOut.println( "+------------------------+" );
fileOut.println( "| |" );
fileOut.println( "| CORNER STORE |" );
fileOut.println( "| |" );
fileOut.println( "| 2016-01-25 04:38PM |" );
fileOut.println( "| |" );
fileOut.println( "| Gallons: " + String.format("%14s", numGallons) + "|" );
fileOut.println( "| Price/gallon: $ " + String.format("%7s", price) + "|" );
fileOut.println( "| |" );
fileOut.println( "| Fuel total: $ " + String.format("%02.02f", price * numGallons) + " |" );
fileOut.println( "| |" );
fileOut.println( "+------------------------+" );
fileOut.close();
}
}
Output
[121] High Score
Goal: Write to a file in a practical application.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: High Score
/// File Name: HighScore.java
/// Date Finished: Mar 02, 2016
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
public class HighScore {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String fileName = "data.txt";
String name;
int score;
System.out.println("You got a high score!");
System.out.print("What's your name? ");
name = input.next();
System.out.print("What's your score? ");
score = input.nextInt();
System.out.println("Data saved in \"" + fileName + "\"...");
// Doing this will automatically close the writer
try (PrintWriter writer = new PrintWriter(fileName)) {
writer.println(name);
writer.println(score);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
[122] Getting Data from a File
Goal: Actually use that file for something.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: PROGRAM_NAME
/// File Name: DataFromAFile.java
/// Date Finished: Mar 02, 2016
import java.io.File;
import java.util.Scanner;
public class DataFromAFile {
public static void main(String[] args) throws Exception {
String name;
int a, b, c, sum;
System.out.print("Getting name and three numbers from file.....");
Scanner fileIn = new Scanner(new File("name-and-numbers.txt"));
name = fileIn.nextLine();
a = fileIn.nextInt();
b = fileIn.nextInt();
c = fileIn.nextInt();
fileIn.close();
System.out.println("done.");
System.out.println("Your name is: " + name);
sum = a + b + c;
System.out.println(a + " + " + b + " + " + c + " = " + sum);
}
}
Output
[123] Simple File Input
Goal: Read from a preexisting file.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Simple File Input
/// File Name: FileInput.java
/// Date Finished: Mar 02, 2016
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class FileInput {
public static void main(String[] args) {
String fileName = "name.txt";
String name = "";
System.out.println("Reading from \"" + fileName + "\"...");
try (Scanner in = new Scanner(new File(fileName))) {
name = in.nextLine();
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
System.out.println("Your name is " + name);
}
}
Output
[124] Summing Three Numbers from a File
Goal: I think the title explains it all.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Summing Three Numbers
/// File Name: ThreeNums.java
/// Date Finished: Mar 02, 2016
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class ThreeNums {
public static void main(String[] args) {
int n1 = 0, n2 = 0, n3 = 0;
String fileName = "3nums.txt";
System.out.print("Grabbing information from \"" + fileName + "\"... ");
try (Scanner in = new Scanner(new File(fileName))) {
n1 = in.nextInt();
n2 = in.nextInt();
n3 = in.nextInt();
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
System.out.println("DONE");
System.out.println(n1 + " + " + n2 + " + " + n3 + " = " + (n1 + n2 + n3));
}
}
Output
[125] Summing Three Numbers from Any File
Goal: Same as above, but you get to choose the file.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Summing Three Numbers from Any File
/// File Name: ThreeNums2.java
/// Date Finished: Mar 02, 2016
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class ThreeNums2 {
public static void main(String[] args) {
Scanner userIn = new Scanner(System.in);
String choice = "";
String file1 = "3nums1.txt", file2 = "3nums2.txt", file3 = "3nums3.txt";
System.out.println("Choose which file to read numbers from (\"" + file1 + "\", \"" + file2 + "\", \"" + file3 + "\").");
System.out.println("Type \"quit\" to quit.");
while (!choice.equals("quit")) {
System.out.print("> ");
choice = userIn.next();
if (choice.equals(file1) || choice.equals(file2) || choice.equals(file3)) {
sum(choice);
} else if (!choice.equals("quit")) {
System.out.println("Invalid input: " + choice);
}
}
}
public static void sum(String fileName) {
System.out.print("Reading numbers from \"" + fileName + "\"... ");
int n1 = 0, n2 = 0, n3 = 0;
try (Scanner in = new Scanner(new File(fileName))) {
n1 = in.nextInt();
n2 = in.nextInt();
n3 = in.nextInt();
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
System.out.println("DONE");
System.out.println(n1 + " + " + n2 + " + " + n3 + " = " + (n1 + n2 + n3));
}
}
Output
[126] Getting all the Data from a File
Goal: Scan a file and output some cool information about it.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Getting all Data from a File
/// File Name: GettingWholeFile.java
/// Date Finished: Mar 03, 2016
import java.io.File;
import java.util.Scanner;
public class GettingWholeFile {
public static void main(String[] args) throws Exception {
int fourLetter = 0;
int caps = 0;
String fn1 = "some-words.txt";
String fn2 = "src/fileio/_126/GettingWholeFile.java";
Scanner wordReader = new Scanner(new File(fn1));
while(wordReader.hasNext()) {
String w = wordReader.next();
if(w.length() == 4)
fourLetter++;
}
wordReader.close();
Scanner selfInput = new Scanner(new File(fn2));
while(selfInput.hasNext()) {
String token = selfInput.next();
if(Character.isUpperCase(token.charAt(0)))
caps++;
}
selfInput.close();
System.out.println( fourLetter + " four-letter words in " + fn1);
System.out.println( caps + " words start with capitals in " + fn2);
}
// How Can Mirrors Be Real If Out Eyes Aren't Real?
}
Output
[127] Displaying a File
Goal: See the entirety of a file's contents.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Displaying a File
/// File Name: DisplayingAFile.java
/// Date Finished: Mar 03, 2016
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class DisplayingAFile {
public static void main(String[] args) {
Scanner userIn = new Scanner(System.in);
String choice = "";
while (!choice.equals("!quit")) {
System.out.println("Open which file? (type \"!quit\" to quit)");
System.out.print("> ");
choice = userIn.next();
if (!choice.equals("!quit")) {
printContentsOfFile(choice);
}
}
}
public static void printContentsOfFile(String fileName) {
try (Scanner in = new Scanner(new File(fileName))) {
while (in.hasNext()) {
System.out.println(in.nextLine());
}
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
}
}
}
Output
[128] Summing Several Numbers from Any File
Goal: Same as #125, but there are an unknown amount of numbers per file.
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Summing Several Numbers from Any File
/// File Name: Summing3.java
/// Date Finished: Mar 03, 2016
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Summing3 {
public static void main(String[] args) {
Scanner userIn = new Scanner(System.in);
String choice;
while (true) {
System.out.println("Which file do you want to read numbers from? (\"!quit\" to quit)");
System.out.println("(\"4nums.txt\", \"5nums.txt\", \"6nums.txt\")");
System.out.print("> ");
choice = userIn.next();
System.out.println();
if (choice.equals("!quit")) {
break;
}
sumNumbers(choice);
}
}
public static void sumNumbers(String fileName) {
try (Scanner in = new Scanner(new File(fileName))) {
System.out.println("Reading from " + fileName + "...");
int total = 0;
while (in.hasNext()) {
int n = in.nextInt();
System.out.print(n + " ");
total += n;
}
System.out.println();
System.out.println("Total is " + total + "\n");
} catch (FileNotFoundException e) {
System.out.println("File does not exist: " + fileName);
}
}
}
Output
[129] Simple Web Input
Goal: Read from the INTERNET!
/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: PROGRAM_NAME
/// File Name: SimpleWebInput.java
/// Date Finished: Mar 03, 2016
import java.net.URL;
import java.util.Scanner;
public class SimpleWebInput {
public static void main(String[] args) throws Exception {
URL mURL = new URL("https://gist.githubusercontent.com/whizvox/ac8fd389ea2459924bf9/raw/b5eefcb1fb7ee21240501d2e2aa82c0e5d6cb62c/gistfile1.txt");
Scanner webIn = new Scanner(mURL.openStream());
while (webIn.hasNext()) {
System.out.println(webIn.nextLine());
}
webIn.close();
}
}
Output
