public abstract class InputStream implements Closeable {
	// 对象要实现 InputStream 的类，
	// 需要实现下面的方法。
	public abstract int read() throws IOException
}

public FileInputStream(File file) throws FileNotFoundException {
	// FileInputStream 类并没有存储 file 引用，只是使用了
	// file.getPath() 来获得文件的存储路径。
    String name = (file != null ? file.getPath() : null);
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
        security.checkRead(name);
    }
    if (name == null) {
        throw new NullPointerException();
    }
    if (file.isInvalid()) {
        throw new FileNotFoundException("Invalid file path");
    }
    
    // 创建 FileDescriptor 对象，
    fd = new FileDescriptor();
    fd.incrementAndGetUseCount();
    
    this.path = name;
    
    // 打开文件
    open(name);
}

private native void open(String name) throws FileNotFoundException

public class Hello{
	private static native void say();
	public static void main(String[] args){
		say();
	}
}

public void set(T value) {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
        map.set(this, value);
    else
        createMap(t, value);
}