java基础——java I/O学习笔记2

package java.io;

public abstract class InputStream implements Closeable {

//最大跳过的缓冲区大小
private static final int MAX_SKIP_BUFFER_SIZE = 2048;
//从输入的流中读取下一个字节
public abstract int read() throws IOException;
//从输入流中读取一定大小的字节，没有数据返回-1
public int read(byte b[]) throws IOException {
return read(b, 0, b.length);
}
//从输人流中读取的数据放到b数组中起始位置为off，长度为len
public int read(byte b[], int off, int len) throws IOException {
if (b == null) {
throw new NullPointerException();
} else if (off < 0 || len < 0 || len > b.length - off) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}

int c = read();
if (c == -1) {
return -1;
}
b[off] = (byte)c;

int i = 1;
try {
for (; i < len ; i++) {
c = read();
if (c == -1) {
break;
}
b[off + i] = (byte)c;
}
} catch (IOException ee) {
}
return i;
}

//跳过输入流的长度为n字节
public long skip(long n) throws IOException {

long remaining = n;
int nr;

if (n <= 0) {
return 0;
}

int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
byte[] skipBuffer = new byte[size];
while (remaining > 0) {
nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
if (nr < 0) {
break;
}
remaining -= nr;
}

return n - remaining;
}
//返回从输入流中可以读取的数据
public int available() throws IOException {
return 0;
}
//关闭输入流，释放任何与这个流有关的资源
public void close() throws IOException {}
//标记在这个输入流的当前位置
public synchronized void mark(int readlimit) {}
//返回到最近标记的位置
public synchronized void reset() throws IOException {
throw new IOException("mark/reset not supported");
}
//测试这个输入流是否支持标记或者重置方法
public boolean markSupported() {
return false;
}

}