java File读写

import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;/** * @author pc2013 *  */public class File001 {/** * @param args */public static void main(String[] args) {BufferedWriter bw = null;BufferedReader br = null;try {File file = new File("d:" + File.separator + "test.txt");if (file.exists()) {System.out.println("file exist");if (file.canExecute()) {System.out.println("this is a executive file");}if (file.canRead()) {System.out.println("this file can be read");}if (file.canWrite()) {System.out.println("this file can be write");}} else {System.out.println("file not exist");boolean flag = file.createNewFile();if (flag == true) {System.out.println("the file test.txt created successfully");} else {System.out.println("file created failure");}}br = new BufferedReader(new FileReader(file));StringBuffer sb = new StringBuffer();String str = null;if (file.length() == 0) {System.out.println("the file is empty" + file.length());} else {System.out.println("the file takes up " + file.length()+ " bytes");while ((str = br.readLine()) != null) {sb.append(str);}}bw = new BufferedWriter(new FileWriter(file));bw.write(sb.toString());for(int i = 0; i < 30; ++i) {bw.write("this is the test date");}System.out.println("write complete, the file takes up " + file.length() + " bytes");} catch (Exception e) {e.printStackTrace();} finally {if (br != null) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (bw != null) {try {bw.close();} catch (IOException e) {e.printStackTrace();}}}}}