IO流（FileOutputStream）
- 写入文件
public class Demo1_IO {
public static void main(String[] args) throws Exception {
FileOutputStream fos = new FileOutputStream("aaa.txt"); // 如果aaa.txt不存在则创建一个
fos.write(97); // 写出的是int类型，文件中保存的是通过字码表中对应的字符
fos.write(98);
fos.write(99);
fos.close();
// 每次打开文件则会将文件重写
}
}
- 追加写入
public class Demo1_File {
public static void main(String[] args) throws IOException {
FileOutputStream fos = new FileOutputStream("aaa.txt", true); // 将第二个参数填写为true则在原有文件中追加内容
fos.write(97); // 写出的是int类型，文件中保存的是通过字码表中对应的字符
fos.write(98);
fos.write(99);
fos.close();
}
}
- 复制文件
public class Demo1_File {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("aaa.txt");
FileOutputStream fos = new FileOutputStream("bbb.txt");
int b;
while ((b = fis.read()) != -1) {
fos.write(b);
}
fis.close();
fos.close();
}
}
- 一次性拷贝文件（消耗内存大）==当文件过大时不宜使用==
public class Demo1_File {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("aaa.txt");
FileOutputStream fos = new FileOutputStream("bbb.txt");
byte[] arr = new byte[fis.available()];
fis.read(arr);
fos.write(arr);
fis.close();
fos.close();
}
}
- 分步拷贝文件（适合拷贝大文件）
public class Demo1_File {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("aaa.txt");
FileOutputStream fos = new FileOutputStream("bbb.txt");
// 读取步长
int size = (int) new File("aaa.txt").length();
byte[] arr = new byte[size];
int len;
while ((len = fis.read(arr)) != -1) {
fos.write(arr);
}
fis.close();
fos.close();
}
}
- BufferedInputStream和BufferedOutputStream
public class Demo1_File {
public static void main(String[] args) throws IOException {
File sourceFile = new File("aaa.txt");
if (!sourceFile.isFile()) {
throw new IOException("拷贝源必须是文件");
}
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceFile.getAbsoluteFile()));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("bbb.txt"));
int b;
while ((b = bis.read()) != -1) {
bos.write(b);
bos.flush(); // 实时刷新
}
bis.close();
bos.close();
}
}
- try finally处理流 流程
File sourceFile = new File("aaa.txt");
// Java 1.7版本
try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceFile.getAbsoluteFile()));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("bbb.t"));) {
int b;
while ((b = bis.read()) != -1) {
bos.write(b);
bos.flush(); // 实时刷新
}
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(source.getAbsoluteFile()));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(target));
// Java 1.6版本写法
try {
int b;
while ((b = bis.read()) != -1) {
bos.write(b);
bos.flush(); // 实时刷新
}
} finally {
try {
if (bis != null) {
bis.close();
}
} finally {
if (bos != null) {
bos.close();
}
}
}
