java读取资料大全（转）

java读取文件大全（转）
??????????????? line++;
??????????? }
??????????? reader.close();
??????? } catch (IOException e) {
??????????? e.printStackTrace();
??????? } finally {
??????????? if (reader != null) {
??????????????? try {
??????????????????? reader.close();
??????????????? } catch (IOException e1) {
??????????????? }
??????????? }
??????? }
??? }

??? /**
???? * 随机读取文件内容
???? */
??? public static void readFileByRandomAccess(String fileName) {
??????? RandomAccessFile randomFile = null;
??????? try {
??????????? System.out.println("随机读取一段文件内容：");
??????????? // 打开一个随机访问文件流，按只读方式
??????????? randomFile = new RandomAccessFile(fileName, "r");
??????????? // 文件长度，字节数
??????????? long fileLength = randomFile.length();
??????????? // 读文件的起始位置
??????????? int beginIndex = (fileLength > 4) ? 4 : 0;
??????????? // 将读文件的开始位置移到beginIndex位置。
??????????? randomFile.seek(beginIndex);
??????????? byte[] bytes = new byte[10];
??????????? int byteread = 0;
??????????? // 一次读10个字节，如果文件内容不足10个字节，则读剩下的字节。
??????????? // 将一次读取的字节数赋给byteread
??????????? while ((byteread = randomFile.read(bytes)) != -1) {
??????????????? System.out.write(bytes, 0, byteread);
??????????? }
??????? } catch (IOException e) {
??????????? e.printStackTrace();
??????? } finally {
??????????? if (randomFile != null) {
??????????????? try {
??????????????????? randomFile.close();
??????????????? } catch (IOException e1) {
??????????????? }
??????????? }
??????? }
??? }

??? /**
???? * 显示输入流中还剩的字节数
???? */
??? private static void showAvailableBytes(InputStream in) {
??????? try {
??????????? System.out.println("当前字节输入流中的字节数为:" + in.available());
??????? } catch (IOException e) {
??????????? e.printStackTrace();
??????? }
??? }

??? public static void main(String[] args) {
??????? String fileName = "C:/temp/newTemp.txt";
??????? ReadFromFile.readFileByBytes(fileName);
??????? ReadFromFile.readFileByChars(fileName);
??????? ReadFromFile.readFileByLines(fileName);
??????? ReadFromFile.readFileByRandomAccess(fileName);
??? }
}

?

5、将内容追加到文件尾部

public class AppendToFile {
??? /**
???? * A方法追加文件：使用RandomAccessFile
???? */
??? public static void appendMethodA(String fileName, String content) {
??????? try {
??????????? // 打开一个随机访问文件流，按读写方式
??????????? RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");
??????????? // 文件长度，字节数
??????????? long fileLength = randomFile.length();
??????????? //将写文件指针移到文件尾。
??????????? randomFile.seek(fileLength);
??????????? randomFile.writeBytes(content);
??????????? randomFile.close();
??????? } catch (IOException e) {
??????????? e.printStackTrace();
??????? }
??? }

??? /**
???? * B方法追加文件：使用FileWriter
???? */
??? public static void appendMethodB(String fileName, String content) {
??????? try {
??????????? //打开一个写文件器，构造函数中的第二个参数true表示以追加形式写文件
??????????? FileWriter writer = new FileWriter(fileName, true);
??????????? writer.write(content);
??????????? writer.close();
??????? } catch (IOException e) {
??????????? e.printStackTrace();
??????? }
??? }

??? public static void main(String[] args) {
??????? String fileName = "C:/temp/newTemp.txt";
??????? String content = "new append!";
??????? //按方法A追加文件
??????? AppendToFile.appendMethodA(fileName, content);
??????? AppendToFile.appendMethodA(fileName, "append end. \n");
??????? //显示文件内容
??????? ReadFromFile.readFileByLines(fileName);
??????? //按方法B追加文件
??????? AppendToFile.appendMethodB(fileName, content);
??????? AppendToFile.appendMethodB(fileName, "append end. \n");
??????? //显示文件内容
??????? ReadFromFile.readFileByLines(fileName);
??? }
}