目录
字符
在处理文件读写的时候，如果是在字节层面进行操作，那么不会涉及字符编码问题；而如果需要在字符层面进行读写的话，就需要明确字符的编码方式也就是字符集了。
static void writeHello() throws IOException {
Files.deleteIfExists(Paths.get("hello.txt"));
Files.write(Paths.get("hello.txt"), "你好hi".getBytes(Charset.forName("GBK")));
System.out.println(Files.readAllBytes(Paths.get("hello.txt")));
}
static void readHello() throws Exception {
char[] chars = new char[10];
String content = "";
try (FileInputStream fileInputStream = new FileInputStream("hello.txt");
InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, Charset.forName("GBK"))) {
int count;
while ((count = inputStreamReader.read(chars)) != -1) {
content += new String(chars, 0, count);
}
}
System.out.println(content);
}
读写操作
注意流的关闭
使用缓冲区
static void writeSrc() throws IOException {
List<String> list = new ArrayList<>();
for (int i = 1; i <= 1000000; i++) {
String s = UUID.randomUUID().toString();
list.add(s);
}
Files.write(Paths.get("src.txt"), list, UTF_8, CREATE, TRUNCATE_EXISTING);
}
//不推荐
static void readSrc() throws Exception {
try (FileInputStream fileInputStream = new FileInputStream("src.txt");
FileOutputStream fileOutputStream = new FileOutputStream("dest.txt")) {
int i;
while ((i = fileInputStream.read()) != -1) {
fileOutputStream.write(i);
}
}
}
//推荐
static void readSrc2() throws Exception {
try (FileInputStream fileInputStream = new FileInputStream("src.txt");
FileOutputStream fileOutputStream = new FileOutputStream("dest.txt")) {
byte[] buffer = new byte[8192];
int len = 0;
while ((len = fileInputStream.read(buffer)) != -1) {
fileOutputStream.write(buffer, 0, len);
}
}
}
//推荐
static void readSrc3() throws IOException {
try (BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("src.txt"));
BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("dest.txt"))) {
byte[] buffer = new byte[8192];
int len = 0;
while ((len = bufferedInputStream.read(buffer)) != -1) {
bufferedOutputStream.write(buffer, 0, len);
}
}
}
//文件复制推荐 transferTo采用流复制
static void readSrc4() throws IOException {
FileChannel in = FileChannel.open(Paths.get("src.txt"), StandardOpenOption.READ);
FileChannel out = FileChannel.open(Paths.get("dest.txt"), CREATE, WRITE);
in.transferTo(0, in.size(), out);
}