关于IO

                br = new BufferedReader(new FileReader(sourceFile));
                bw = new BufferedWriter(new FileWriter(destFile));
                String source = "";
                while ((source = br.readLine()) != null) {
                 String replaceSrc = replace(source);
                  //bw.write(replace(source) + "/r/n");
                 bw.write(replaceSrc+"/r/n");
                 source = null;    
                }
                br.close();
                bw.close();

 

与

                while ((source = br.readLine()) != null) {
                  bw.write(replace(source) + "/r/n");
                }

有什么区别呢