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• Quiz 2 Grades Posted on blackboard

Files• Data in Main Memory is “volatile”

• File: Place for “permanent” data storage

• C: drive, A: drive, Flash drive, etc.

Disk

File

Main Memory

main()

int num;

string firstname;

Scanner Input

Scanner scan = new Scanner(System.in);

while (scan.hasNextInt())

{

i = scan.nextInt();

}

// System.in is the keyboard “file”

Input Filesimport java.io.*;import java.util.Scanner;

class FileInput{public static void main(String [ ] args) throws IOException{File ifile = new File("data.txt");Scanner scan = new Scanner(ifile);while (scan.hasNextInt()){

i = scan.nextInt(); }}}

176432

data.txt file

Display Output

for (i=0;i < 100; i = i + 2)

{

System.out.println(i);

}

// System.out is the display window “file”

Output File Streamsimport java.io.*;class FileOutput{public static void main(String [ ] args) throws IOException{int i;FileOutputStream ofile = new FileOutputStream("data2.txt",false); //true:APPPrintWriter pw = new PrintWriter(ofile);for (i=0;i < 100; i = i + 2){pw.println(i);}pw.close(); // Writes data to file on disk

}}

02…98

data2.txt

import java.util.Scanner;import java.io.*; class FormatFileData{public static void main(String [ ] args) throws IOException{

int loops, integer, i;float decimal;String name;

File ifile = new File("mydata.txt");Scanner scan = new Scanner(ifile);loops = scan.nextInt();for(i= 0 ; i < loops; i++){integer = scan.nextInt();decimal = scan.nextFloat();name= scan.next();System.out.print(integer + " ");System.out.print(decimal + " ");System.out.print(name + " ");System.out.println();}

}}

mydata.txt file

58 9.3 Jon6 14.335 Bill0 35.67e9 Mary-23 -4.55 Smith-3 -4e3 xyz

8 9.3 Jon6 14.335 Bill0 3.567E10 Mary-23 -4.55 Smith-3 –4000.0 xyz

Output: