import java.io.*;
	
	
	public class TextFileIO{
	
		public static void main(String[] args) {
			
	//		*************************************************************************
	//			READING FROM COMMAND LINE
			
			String commandLineInput;
			BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
	
		    try {
		    	commandLineInput = bufferedReader.readLine();
		        }
				catch (IOException e) {
			           e.printStackTrace();
			           System.exit(1);
				}
	
	//		****************************************************************
	//			READING FROM FILE LINE BY LINE
	
			String readLine;
		    try{
		    	BufferedReader reader = new BufferedReader(new FileReader ("input.txt"));
		    	try{
		    		readLine=reader.readLine();
		    		//now you have the first line of the file in readLine variable.
		    			
		    		while(readLine!=null){
		    			// in this while loop you read the rest of the file
		    			// line by line till you get to the end of the file
		    			// you can do what you want to do with the text of the file here
		    			// e.g., by sending the text as an argument of a method
		    			// e.g., doSomeProcessOn(readLine);
		    			readLine= reader.readLine();
		    			
		    		}		                     
					}catch(IOException e){
						e.printStackTrace();
					}
		    }catch(FileNotFoundException e){
		    	e.printStackTrace();
		    }
	
	//	    ****************************************************************    
	//	  	  	WRITING TO FILE LINE BY LINE
	    
		    String outputString = "Whatever you want to write in the file in a single line";
		    try {
		    	BufferedWriter outputFile = new BufferedWriter(new FileWriter("output.txt"));
		             
	            outputFile.write(outputString);
		        outputFile.newLine();//going to the next line.
		        outputFile.close(); // It is important to close the output file.
			}catch(IOException e){
				e.printStackTrace();
			}
		}
	}