import java.io.*;
import java.util.*;


class Main{	
	
	
	
//Ex1
	
	
	static public void Ex1 (String arg[]) {
		File f1 = new File ("Ex1Swap1.txt");
		File f2 = new File ("Ex1Swap2.txt");
	
		int i = 1;
		int j = 2;
		System.out.println("Start:\ni = " + i + " and j = " + j);
		
//	//HOW TO SWAP?
//		int tmp=0;
//	
//		System.out.println("First step:\ni = " + i + "\nj = " + j + "\ntmp = "+ tmp);
//		tmp = i;
//		System.out.println("Second step:\ni = " + i + "\nj = " + j + "\ntmp = "+ tmp);
//		i=j;
//		System.out.println("Third step:\ni = " + i + "\nj = " + j + "\ntmp = "+ tmp);
//		j= tmp;
//		System.out.println("Fourth  step:\ni = " + i + "\nj = " + j + "\ntmp = "+ tmp);
//		System.out.println("End:\ni = " + i + " and j = " + j);

	
		//we want to do the same with files

		//However the File method renameTo() has weel-known problem on Windows
		//It can not rename existing files...
		//this my solution to this problem: create new files

		//I create two new File object tmp1 and tmp2 which will be the new names of f1 and f2
		f1.renameTo(new File ("tmp1"));
		f2.renameTo(new File ("tmp2"));
		
		//to operate on these new files i create two new File objects

		File tmp1 = new File ("tmp1");
		File tmp2 = new File ("tmp2");
		
		//then again, i create two new File objects and I rename tmp's with these names
		tmp1.renameTo(new File ("Ex1Swap2.txt"));
		tmp2.renameTo(new File ("Ex1Swap1.txt"));
		
		//here I used some string because the name of the files are given,
		//but you can have a more general method recording the two file name
		//in string created by using the getName() method		

	
	
	
//Ex2
	
	
    public static void Ex2() throws Exception{
    	//create the file and use it to create the scanner
    	
    	File gar = new File ("Garbage.txt");
    	Scanner sGar = new Scanner(gar);
    	
    	//print the next line untill the end of the file
    	while(sGar.hasNext()) {
    	System.out.println(sGar.nextLine());
    	}
    	sGar.close();
    	//close the scanner
    	
    	
    	//open a writer, write the sentence and close it
    	
    	PrintWriter pGar = new PrintWriter(gar);
    	pGar.println("I am going to be erased");
    	pGar.close();
    	
    	//open a NEW scanner for read the new content of the file, print it and then close
    	Scanner newSGar = new Scanner(gar);
    	while(newSGar.hasNext()) {
    	System.out.println(newSGar.nextLine());
    	}
    	newSGar.close();
    	
    	
    	//delede the file
    	gar.delete();
    	
    	//just a message
    	System.out.println("Has Garbage.txt been removed? " + gar.exists());
    	

    	
    }
	

	
//EX3: COPY EVEN LINES
	
	
    public static void Ex3() throws Exception{
	int i = 1;	
	File fa = new File("a.txt");
	File fb = new File("b.txt");
	
	
	//create a scanner which reads the file fa
	Scanner sa = new Scanner (fa);
	
	//create a printwriter which writes in the file fb
	PrintWriter pb= new PrintWriter(fb);
	
	//starting the loop: untill there is something to read
		while (sa.hasNext()) {
	//verify if I am in a even line (see counter i), in this case I write the line in b
			if(i % 2==0) {
				pb.println(sa.nextLine());
				}
	//increase the line counter
			i++;
    	}
		
	//close the scanner and the printer
	   sa.close();
	   pb.close();
    
    }
 





//Ex4

	public static void Ex4() throws Exception{
		Scanner user = new Scanner(System.in);
		
		//scan the name of the two files
		
		System.out.println("Give the name of the file to be processed: ");
		String name1 = user.nextLine();
		
		System.out.println("Give the name of the output file: ");
		String name2 = user.nextLine();
		
		
		//create the File objects for these files
		File f1 = new File (name1);
		File f2 = new File (name2);
		
		
		//use the first to create a scanner and the second for the printer
		Scanner s1 = new Scanner(f1);
		PrintWriter p2 = new PrintWriter (f2);
		
		
		//set the counters and allocate a variable for string references
		int linesCounter=0;
		int charactersCounter = 0;
		String s;
		 
		
		//scan the file until the end, increase the line number every newline and
		//character counter by adding the lenght of each line
		while (s1.hasNext()) {
			s=s1.nextLine();
			charactersCounter = charactersCounter+s.length();
			linesCounter++; 
       }
		
		//use the data to print the content in the file
		p2.println("File name:" + name1);
		p2.println("Number of lines: " + linesCounter + "\nNumber of characters: " + charactersCounter);
		
		
		//remember to close all the scanners/printers
		s1.close();
		p2.close();
		user.close();
		
	}




//Ex5:


	public static void Ex5() throws Exception{
		
		//create scanner and printer directly (one single passage)
		PrintWriter pA = new PrintWriter(new File("A.txt"));
		Scanner sB =new Scanner(new File("B.txt"));
		Scanner sC =new Scanner(new File("C.txt"));
				
		//scan the file B and C until one of the two is non-empty
		//and write the newline in A (an empty line when the file finish)
		
		while( sB.hasNext() && sC.hasNext() ) {
			if(sB.hasNext()) {
				pA.println(sB.nextLine());
			}else {
				pA.println("");
			}
			if(sC.hasNext()) {
				pA.println(sC.nextLine());
			}else {
				pA.println("");
			}
		}
		pA.close();
		sB.close();
		sC.close();
		
	}

}