FileInputStream与BufferedInputStream有哪些区别？

区别一：FileInputStream是InputStream的子类，而BufferedInputStream的子类，是InputStream的间接子类 代码依据： FileInputStream: public class FileInputStream extends InputStream{}

BufferedInputStream : public class BufferedInputStream extends FilterInputStream {}

区别二：他们两个在使用执行read()方法时，低层的实现各不相同：FileInputStream是直接从磁盘读取数据至内存；而 BufferedInputStream是直接从缓冲区获取数据，它的底层是维护了一块缓冲区域，它存在于内存中，其容量是8192个字节， 然后每次读取内容时，直接从这片缓冲区读取内容，这样它的效率较快；

代码依据： FileInputStream： public int read() throws IOException { return read0(); } private native int read0() throws IOException;//本地方法，直接与操作系统交互

BufferedInputStream : public synchronized int read() throws IOException { if (pos >= count) { fill();//一旦缓冲区的内容不足，就调用fill()方法，充满这片缓冲区 if (pos >= count) return -1; } return getBufIfOpen()[pos++] & 0xff; }

private void fill() throws IOException { byte[] buffer = getBufIfOpen(); if (markpos < 0) pos = 0; else if (pos >= buffer.length) if (markpos > 0) { int sz = pos - markpos; System.arraycopy(buffer, markpos, buffer, 0, sz); pos = sz; markpos = 0; } else if (buffer.length >= marklimit) { markpos = -1; pos = 0; } else if (buffer.length >= MAX_BUFFER_SIZE) { throw new OutOfMemoryError("Required array size too large"); } else { int nsz = (pos <= MAX_BUFFER_SIZE - pos) ? pos * 2 : MAX_BUFFER_SIZE; if (nsz > marklimit) nsz = marklimit; byte nbuf[] = new byte[nsz]; System.arraycopy(buffer, 0, nbuf, 0, pos); if (!bufUpdater.compareAndSet(this, buffer, nbuf)) { throw new IOException("Stream closed"); } buffer = nbuf; } count = pos; int n = getInIfOpen().read(buffer, pos, buffer.length - pos); if (n > 0) count = n + pos; }

private byte[] getBufIfOpen() throws IOException { byte[] buffer = buf; if (buffer == null) throw new IOException("Stream closed"); return buffer; } private static int DEFAULT_BUFFER_SIZE = 8192;//缓冲区的默认容量是8192； /*补充： 1.BufferedInputStream 使用了装饰器模式 2.它的底层仍旧自动调用了FileInputStream底层的rean0()方法，只不过它在读取数据之前底层就提前调用了， 它把数据读到缓冲区，这样内存读取数据时，就可以直接从缓冲区里读取，效率更快 */