java.nio.Buffer源码解读

版本：JDK7package java.nio;public abstract class Buffer {    // mark <= position <= limit <= capacity    private int mark = -1;// 标记，一个特定的position，通过mark()方法指定Buffer中的标记，之后可以通过reset()方法恢复到这个索引位置    private int position = 0;// 下一个要读取或写入的数据的索引    private int limit;// 界限，表示缓冲区中可操作数据的大小，索引等于和大于limit的数据不能进行读写。    private int capacity;// 缓冲区的容量，创建后不能修改。    // Used only by direct buffers    // NOTE: hoisted here for speed in JNI GetDirectBufferAddress    long address;    // Creates a new buffer with the given mark, position, limit, and capacity,    Buffer(int mark, int pos, int lim, int cap) {        if (cap < 0) throw new IllegalArgumentException("Negative capacity: " + cap);        this.capacity = cap;        limit(lim);        position(pos);        if (mark >= 0) {            if (mark > pos)                throw new IllegalArgumentException("mark > position: (" + mark + " > " + pos + ")");            this.mark = mark;        }    }    public final int capacity() {        return capacity;    }    public final int position() {        return position;    }// 重新设置position的值    public final Buffer position(int newPosition) {        if ((newPosition > limit) || (newPosition < 0)) throw new IllegalArgumentException();        position = newPosition;        if (mark > position) mark = -1;        return this;    }    public final int limit() {        return limit;    }// 重新设置limit的值：如果新limit小于position，则将position设为新limit    public final Buffer limit(int newLimit) {        if ((newLimit > capacity) || (newLimit < 0)) throw new IllegalArgumentException();        limit = newLimit;        if (position > limit) position = limit;        if (mark > limit) mark = -1;        return this;    }// 设置标记    public final Buffer mark() {        mark = position;        return this;    }// 将position的值设置为mark    public final Buffer reset() {        int m = mark;        if (m < 0)            throw new InvalidMarkException();        position = m;        return this;    }// 清空缓冲区：Buffer的属性恢复到初始化状态。注意：此时缓冲区中的数据仍然存在。    public final Buffer clear() {        position = 0;        limit = capacity;        mark = -1;        return this;    }// 将limit设为当前的position，之后将position重置为0    public final Buffer flip() {        limit = position;        position = 0;        mark = -1;        return this;    }// 将position设为0，并取消设置的标记：即重新读Buffer    public final Buffer rewind() {        position = 0;        mark = -1;        return this;    }// 返回剩余的可用空间    public final int remaining() {        return limit - position;    }// 判断缓冲区中是否还有元素    public final boolean hasRemaining() {        return position < limit;    }    public abstract boolean isReadOnly();    public abstract boolean hasArray();    public abstract Object array();       public abstract int arrayOffset();    public abstract boolean isDirect();    // -- Package-private methods for bounds checking, etc. --// ...}