1. Computer Science A 11: 24/3

2. Files and Input/Output Get information about a file : File f= new File("data.txt"); if(f.exists()) System.out.println("file exists"); if(f.isDirectory()){ System.out.println("is directory"); String[] lst=f.list(); for(String s:lst) System.out.println("file: "+s); }

3. Reading text from a file ArrayList data=new ArrayList (); try{ File f= new File("data.txt”); BufferedReader in= new BufferedReader(new FileReader(f)); while(true){ String s=in.readLine(); if(s==null)break; data.add(s); } in.close(); }catch(Exception e){ System.out.println("Couldn't open file data.txt"); }

4. Writing text to a file try{ File f= new File("data.txt"); PrintWriter out= new PrintWriter(new FileWriter(f)); for(String s:data) out.println(s); }catch(Exception e){ System.out.println("Couldn't open file data.txt");} }

5. Iist all files in a directory tree static void listFiles(String d){ File f=new File(d); System.out.println(d); if(!f.isDirectory())return; String[] lst=f.list(); for(String s:lst)listFiles(d+"/"+s); }.. listFiles(".");