Experiment 9 input and output stream (excerpt)

Experiment 9 I / O stream

The experiment purpose

1. understand Java In the technical system “ flow ” The concept of .

2. master System.in and System.out The basic use method

3. Master the common classes and usage methods of byte stream and character stream .

4. master Java The basic operation of the program on the file .

Experimental hours 4 Class hours

Experimental content

1. Write programs using System.in Object's read() Method read keyboard input , When the program is running , First, ask the number of data you need to input , Then input the integer of the specified number in turn , After input , Output the sum of all input integers .

package code91;
import java.io.BufferedReader;  // Character input stream with buffer function 
import java.io.IOException;
import java.io.InputStreamReader;  // Byte stream to character stream converted stream 
public class code91 {

	public static void main(String[] args)throws NumberFormatException,Exception {
		// TODO  Automatically generated method stubs 
		int a[]=new int[512];  // Create an input stream that receives keyboard input data 
		int sum=0;
		InputStreamReader c = new InputStreamReader(System.in);  // Put the input stream into the buffer stream 
		BufferedReader d = new BufferedReader(c);
		System.out.println(" Please enter the total number of numbers :");
		int n=Integer.parseInt( d.readLine());  // Convert to basic data type int
		System.out.println(" These numbers are :");
		for(int i=0;i<n;i++) {
			int b=Integer.parseInt(d.readLine());
			a[i]=b;
			sum+=a[i];
		}
		System.out.println(" The sum of all input numbers is :"+sum);

	}

}

2. On computer D Create a disk named FileList Text file for , take D Save the names of all files and folders on the disk to this file .

package code92;
import java.io.File;
import java.io.FileWriter;
public class code92 {

	public static void main(String[] args) {
		// TODO  Automatically generated method stubs 
		try {
			File f=new File("D:\\FileList");
			if(!f.exists()){
			f.createNewFile();  // Create a text file 
			}
			else {
				System.out.println(" file already exist ");
			}
			File file=new File("D:\\");
			File[] fs=file.listFiles();
			FileWriter out = new FileWriter(f);
			for(File fs1 : fs) {
				out.write(fs1.getPath()+'\r'+'\n');
			}
			out.close();
		}catch(Exception e) {
			e.printStackTrace();
		}

	}

}

5. Important files usually need to be encrypted , Please write a program to encrypt text files , The password table is as follows , If the plaintext is in capital letters, the ciphertext is also in capital letters corresponding to the password table , If the plaintext is in lowercase letters, the ciphertext is also in lowercase letters corresponding to the password table .

Plaintext

A

B

C

D

E

F

G

H

I

J

K

L

M

Ciphertext

T

O

I

A

N

D

E

G

H

Z

B

K

F

Plaintext

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Ciphertext

J

M

C

L

P

Y

V

X

Q

R

W

U

S

package code95;
import java.io.File;
import java.io.FileReader;  // File character input stream 
import java.io.FileWriter;  // File character output stream 
import java.util.Scanner;
public class code95 {
 
	public static void main(String[] args) throws Exception {
		char reality[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
				'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
		char fake[] = { 'T', 'O', 'I', 'A', 'N', 'D', 'E', 'G', 'H', 'Z', 'B', 'K', 'F', 'J', 'M', 'C', 'L', 'P', 'Y',
				'V', 'X', 'Q', 'R', 'W', 'U', 'S' };  // Create two arrays , Fill in letters and encrypted ciphertext respectively 
		FileWriter fw = new FileWriter(new File("D:\\FileList"));
		FileReader fr = new FileReader(new File("D:\\FileList"));  // Yes, the experiment 2 Encrypt the file created in 
		Scanner in = new Scanner(System.in);
		String str = in.nextLine();
		char[] a = str.toCharArray();  // Convert string to character array 
		for (int n = 0; n < a.length; n++) {
			for (int i = 0; i < 26; i++) {
				if (a[n] == reality[i]) {  // Encrypted letter 
					a[n] = fake[i];
					break;
				} else if (a[n] <= 'z' && a[n] >= 'a') {  // Conversion of lowercase letters to uppercase letters 
					if (reality[i] == (char) (a[n] - 32)) { // Cast 
						a[n] = (char) (fake[i] + 32);  // Convert upper ciphertext to lower case 
						break;
					}
				}
			}
		}
		fw.write(a);
		in.close();
		fw.close();
		fr.close();
	}
 
}