正文
java读取文件(更新jdk7及jdk8)
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以字节的方式读取：
InputStream inputStream = new FileInputStream(file);
int temp = -1;
StringBuilder sb = new StringBuilder();
while((temp = inputStream.read()) != -1){
sb.append((char)temp);
}
inputStream.close();
也可以多个字节一起读取：
InputStream inputStream = new FileInputStream(file);
byte[] bytes = new byte[10];
StringBuilder sb = new StringBuilder();
int length = -1;
while((length = inputStream.read(bytes))!= -1){
sb.append(new String(bytes,0,length,Charset.forName("utf-8")));
}
inputStream.close();
以字符的方式读取：
InputStream inputStream = new FileInputStream(file);
InputStreamReader isr = new InputStreamReader(inputStream,Charset.forName("utf-8"));
StringBuilder sb = new StringBuilder();
int temp = -1;
while((temp = (isr.read()))!= -1){
sb.append((char)temp);
}
inputStream.close();
isr.close();
或者用封装的BufferedReader按行读取，效率更高：
InputStream inputStream = new FileInputStream(file);
InputStreamReader isr = new InputStreamReader(inputStream,Charset.forName("utf-8"));
BufferedReader bufferedReader = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line = null;
while((line = bufferedReader.readLine())!=null){
sb.append(line + '\n');
}
inputStream.close();
isr.close();
bufferedReader.close();
-----------------------------------------------以上是jdk7之前一般使用的读取文件方法-------------------------------------------------------------------------------------------------------
jdk7引入了新的文件api: java.nio.file.Files。 Files.readAllBytes()方法将文件内容全部读入内存，并且确保读取完之后文件是关闭的，也就是说，不用手动调用close方法:
String path = "C:\\test.txt";
System.out.print(Files.readAllBytes(Paths.get(path)));
当文件过大时，不建议使用readAllBytes()方法将文件内容一次全部读入到内存里面。
java8中使用流的方式来读取更高效：
Files.lines(Paths.get(path),StandardCharsets.UTF_8).forEach(System.out::println);
