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Displaying  Source Code(s)  
 

 
copying a file

--------------------------------------------------------------------------------

Description : this code lets one to copy one file into another with options like appending to a file or overwriting a file or creating a new file

/* Copy.java
copies one file to another.
if the destination file exists the user is given the options
to overwrite or append to the the existing file or enter a
new file name or exit.
*/

import java.io.*;

class Copy{
private static FileInputStream fin;
private static FileOutputStream fout;
private static boolean flag;

// creates a new file outputstream instance
static FileOutputStream create(String s) throws IOException{
flag=true;
fout=new FileOutputStream(s);
flag=false;
return fout;
}

// creates a file outputstream instance in append mode
static FileOutputStream append(String s) throws IOException{
return fout=new FileOutputStream(s,true);
}

// displays message if program cannot copy a file
static void nocopy(){
System.out.println("No File Copied");
System.out.println("Thank you for using this program....");
}



public static void main(String args[]) throws IOException{
fin=null;
fout=null;
File f=null;
int i=0;
char ch;
boolean fl=false;
try{
fin=new FileInputStream(args[0]);
f=new File(args[1]);
if(f.isDirectory()){
args[1]+=args[0];
f=new File(args[1]);
}
if(f.exists()){ //outer
if
if(args[0].equals(args[1])){
throw new MyException("File cannot be copied onto
itself!!");
}
System.out.println("'"+args[1]+"' already exists!!");
System.out.println();
if(!f.canWrite()){
System.out.println("'"+args[1]+"' is read-only. Access
denied!!");
System.out.println();
}
else{
System.out.println("Overwrite----------------> o");
System.out.println("Append to existing file--> a");
fl=true;
}
System.out.println("New destination file-----> n");
System.out.println("Exit---------------------> any other
key");
ch=ReadVal.readChar();
switch(ch){ //switch
begins
case 'o':
case 'O':
if(fl)
create(args[1]);
else
throw new MyException("");
break;
case 'a':
case 'A':
if(fl)
append(args[1]);
else
throw new MyException("");
break;
case 'n':
case 'N':
String s;
System.out.print("enter new file name : ");
s=ReadVal.readString();
File f1=new File(s);
if(f1.exists()){
if(args[0].equals(s)){
throw new MyException("File cannot be copied onto
itself!!");
}
if(!f1.canWrite())
throw new MyException("'"+s+"' is read-only. Access
denied!!");
System.out.println("File exists!!");
System.out.print("Overwrite / Append / Exit ? ");
char c;
c=ReadVal.readChar();
if(c=='o' || c=='O')
create(s);
else if(c=='a' || c=='A')
append(s);
else{
nocopy();
System.exit(1);
}
}
if(fout==null)
create(s);
break;
default:
nocopy();
return;
} //switch
ends
} //outer
if
ends

if(fout==null)
create(args[1]);
} //try
ends
catch(ArrayIndexOutOfBoundsException ae){
System.out.println("Usage : java Copy <source file> <destination
file>");
System.out.println("Required parameter(s) missing.");
return;
}
catch(FileNotFoundException fe){
if(flag)
System.out.println("Cannot copy to disk. Access denied!!");
else
System.out.println("Source file does not exist");
nocopy();
return;
}
catch(MyException me){
System.out.println(me);
nocopy();
return;
}

// read from source file & write to destination file
try{
while((ifin.read())!=-1){
fout.write((char)i);
// i=fin.read();
}
fin.close();
fout.close();
}
catch(IOException ie){}
System.out.println("File Copied Successfully");
System.out.println("Thank you for using this program....");
}
}


**********************************************************************



//ReadVal.java

import java.io.*;

public class ReadVal
{
static int readInt(){
int i=0;
try{
BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
i=Integer.parseInt(br.readLine());
}
catch(IOException ie){
System.out.println(ie);
i=0;
}
catch(NumberFormatException ne){
System.out.println("idiot u were asked to enter a
number!!!!");
i=0;
}
return i;
}
static String readString(){
String s="";
try{
BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
s=br.readLine();
}
catch(IOException ie){
System.out.println(ie);
s="";
}
return s;
}
static double readDouble(){
double d=0;
try{
BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
d=Double.parseDouble(br.readLine());
}
catch(IOException ie){
System.out.println(ie);
d=0;
}
catch(NumberFormatException ne){
System.out.println("idiot u were asked to enter a
number!!!!");
d=0;
}
return d;
}
static float readFloat(){
float f=0;
try{
BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
f=Float.parseFloat(br.readLine());
}
catch(IOException ie){
System.out.println(ie);
f=0;
}
catch(NumberFormatException ne){
System.out.println("idiot u were asked to enter a
number!!!!");
f=0;
}
return f;
}

static char readChar(){
char c;
try{
c=readString().charAt(0);
}
catch(StringIndexOutOfBoundsException se){
c=0;
}
return c;
}
}

 

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