Question

Java Code using Stack

Write a program that opens a text file and reads its contents into a stack of characters, it should read character by character (including space/line change) and push into stack one by one. The program should then pop the characters from the stack and save them in a second text file. The order of the characters saved in the second file should be the reverse of their order in the first file.

Ex input file:

Good Morning!

Bye..

EX output file:

!gninroM dooG

...eyB

Answer 1

import java.io.*;
import java.util.*;
class Stack{
    private static int top,maxsize;   
    private static char arr[];
        //Stack creation using arrays.
    Stack(int n){ 
                this.maxsize=n;
        top=-1;         
                arr=new char[maxsize];
    }   
        //push character into stack
    void push(char p){  
        char val=p;  
        top++;  
        arr[top]=val;   
    }   
    //pop character from stack  
    char pop(){   
        char o=arr[top];
        top --;    
        return o;  
    }
} 
public class File1{
        public static void main (String [] args)throws IOException{
                FileReader f=new FileReader("input.txt");
        BufferedReader read=new BufferedReader(f);
        String data;
                try{
                        //creating output file.
                        File fi=new File("output.txt");
                        //if output file exists then it is deleted and creates new one.
                        if(fi.exists()){
                                fi.delete();
                        }
                        FileWriter d=new FileWriter("output.txt",true);
                        while((data=read.readLine())!=null){
                                Stack s=new Stack(data.length());
                                //pushing characters into stack.
                                for(int i=0;i<=data.length()-1;i++){
                                        s.push(data.charAt(i)); 
                                }
                                //writing characters into output file.
                                for(int i=0;i<data.length();i++){
                                        d.write(s.pop());
                                }
                                d.write("\n");
                        }
                        //closing output file to ensure security.
                        d.close();
                }catch(Exception e){System.out.println(e);}
        }
}

Note:- If your input file is in another location i.e., other than current working directory, then please specify path in the above code as follows:-

FileReader f=new FileReader("C:\\Users\\HP\\Desktop\\java\\input.txt");