java读取文件(txt)

FileInputStream
public class FileInputStream extends InputStream
构造方法:
FileInputStream(File file)
FileInputStream(String name)
FileInputStream(FileDescriptor fdObj)

File file=new File("C:\\Test\\Java\\3.txt");
try {
    //方法一
	InputStream fis=new FileInputStream(file);
	System.out.println(fis.available()+"-----"+file.length());
	byte[] b=new byte[fis.available()];//新建一个字节数组
	fis.read(b);//将文件中的内容读取到字节数组中
	String str2=new String(b,"GBK");//再将字节数组中的内容转化成字符串形式输出
	System.out.println(str2);
	fis.close();
	//方法二
    /*
    int i =0;//			
	InputStream is = new FileInputStream(file);		
	byte[] b=new byte[is.available()];//新建一个字节数组
	byte c = (byte)is.read(); 
	while(c != -1){ 
		b[i] = c;
		i++; 
		c = (byte)is.read(); 
	}
	System.out.println(new String(b,"GBK"));
    */
} catch (FileNotFoundException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
} catch (IOException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
}

InputStreamReader
public class InputStreamReader extends Reader
构造方法:
InputStreamReader(InputStream in)
InputStreamReader(InputStream in, Charset cs)
InputStreamReader(InputStream in, CharsetDecoder dec)
InputStreamReader(InputStream in, String charsetName) 
处理的不太完美，一个一个输出的，有待解决

try {
	InputStreamReader isr=new InputStreamReader(new FileInputStream("C:\\Test\\Java\\3.txt"),"GBK");
	int ch=0;
	while((ch=isr.read())!=-1){
		System.out.println((char)ch);
	}
} catch (FileNotFoundException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
} catch (IOException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
}

FileReader
public class FileReader extends InputStreamReader
构造方法:
FileReader(File file)
FileReader(FileDescriptor fd)
FileReader(String fileName)
乱码问题未解决，有待解决

try {
	FileReader fr=new FileReader("C:\\Test\\Java\\3.txt");
	int c=0;
	while((c=fr.read())!=-1){
		System.out.println((char)c);
	}
} catch (FileNotFoundException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
} catch (IOException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
}

BufferedReader[推荐使用]
public class BufferedReader extends Reader
构造方法:
BufferedReader(Reader in)
BufferedReader(Reader in, int sz)

try {
	BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream("C:\\Test\\Java\\3.txt"),"GBK"));
    //BufferedReader br=new BufferedReader(new FileReader("C:\\Test\\Java\\3.txt"));
	String str=br.readLine();
	while(str!=null){
		System.out.println(str);
		str=br.readLine();
	}
} catch (FileNotFoundException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
} catch (IOException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
}