将内容追加到文件尾部-采用字符流的形式，将abc.txt中的内容更换为 好好学习，天天向上!

<span style="font-size:18px;">import java.io.File;import java.io.FileReader;import java.io.FileWriter;import java.io.RandomAccessFile;import java.io.Reader;import java.io.Writer;//采用字符流的形式，将abc.txt中的内容更换为  好好学习，天天向上!public class Demo1 {public static void main(String[] args) {// fun1();appendMethodA("./res/abc.txt", "!");}/** * 最原始的添加办法 */private static void fun1() {File file = new File("./res/abc.txt");File file2 = new File("./res/ab.txt");try (Reader is = new FileReader(file);Writer os = new FileWriter(file2);) {char[] buffer = new char[4];int len = -1;while ((len = is.read(buffer)) != -1)os.write(buffer, 0, len);os.write('!');os.flush();} catch (Exception e) {}file.delete();file2.renameTo(new File("./res/abc.txt"));}/** * 将内容追加到文件尾部A *  * @param fileName * @param content */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 (Exception e) {e.printStackTrace();}}/** * 将内容追加到文件尾部B *  * @param fileName * @param content */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 (Exception e) {e.printStackTrace();}}}</span>