（一）JAVA NIO BUFFER

发表于 分类于 阅读次数：
1.变量：

capacity： 指定了可以存储在缓冲区中的最大数据容量，实际上，它指定了底层数组的大小，或者至少是指定了准许我们使用的底层数组的容量。
position： 下一次读取或写入的位置。（每次调用get put方法+1）
limit：指定还有多少数据需要取出，或者还有多少空间可以放入数据。（每次调用get put方法时候，通过position与limit对比）

2.方法：

get：position + 1
put：position + 1
flip：limit = position position = 0 mark = -1
clear：limit = capacity position = 0 mark = -1
mark： mark = position
reset：position = m;
duplicate：浅拷贝（每个缓存区的上界、容量、位置等属性是各自独立的）

3.代码

BufferTest.java

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public class BufferTest {
    public static void main(String[] args) {
        IntBuffer buff = IntBuffer.allocate(10);
        buff.get();
        buff.put(1);
        buff.get();
        buff.put(2);
        buff.get();
        buff.put(3);
        buff.mark();
        buff.get();
        buff.put(4);
        buff.get();
        buff.put(5);
        System.out.println(" ========== init ========== ");
        System.out.println("capacity:\t" + buff.capacity());
        System.out.println("limit:\t" + buff.limit());
        System.out.println("position:\t" + buff.position());
        System.out.println();
        buff.reset();
        System.out.println(" ========== mark reset ========== ");
        System.out.println("capacity:\t" + buff.capacity());
        System.out.println("limit:\t" + buff.limit());
        System.out.println("position:\t" + buff.position());
        System.out.println();
        buff.flip();
        System.out.println(" ========== flip ========== ");
        System.out.println("capacity:\t" + buff.capacity());
        System.out.println("limit:\t" + buff.limit());
        System.out.println("position:\t" + buff.position());
        for (int i = 0; i < buff.limit(); i++) {
            System.out.print(buff.get() + "\t");
        }
        System.out.println();
        System.out.println();
        buff.clear();
        System.out.println(" ========== clear ========== ");
        System.out.println("capacity:\t" + buff.capacity());
        System.out.println("limit:\t" + buff.limit());
        System.out.println("position:\t" + buff.position());
        for (int i = 0; i < buff.limit(); i++) {
            System.out.print(buff.get() + "\t");
        }
        System.out.println();
        System.out.println();

        //重新数据初始化
        System.out.println(" ========== duplicate ========== ");
        buff.clear();
        IntBuffer copyIntBuffer = buff.duplicate();
        buff.get();
        buff.put(2);
        System.out.println(" ========== buff duplicate ========== ");
        System.out.println("capacity:\t" + buff.capacity());
        System.out.println("limit:\t" + buff.limit());
        System.out.println("position:\t" + buff.position());
        System.out.println(buff);
        System.out.println(" ========== copyIntBuffer duplicate ========== ");
        System.out.println("capacity:\t" + copyIntBuffer.capacity());
        System.out.println("limit:\t" + copyIntBuffer.limit());
        System.out.println("position:\t" + copyIntBuffer.position());
        for (int i = 0; i < buff.limit(); i++) {
            System.out.print(copyIntBuffer.get() + "\t");
        }
        System.out.println();
    }
}
4.Console
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 ========== init ========== 
capacity:	10
limit:	10
position:	10

 ========== mark reset ========== 
capacity:	10
limit:	10
position:	6

 ========== flip ========== 
capacity:	10
limit:	6
position:	0
0	1	0	2	0	3	

 ========== clear ========== 
capacity:	10
limit:	10
position:	0
0	1	0	2	0	3	0	4	0	5	

 ========== duplicate ========== 
 ========== buff duplicate ========== 
capacity:	10
limit:	10
position:	2
java.nio.HeapIntBuffer[pos=2 lim=10 cap=10]
 ========== copyIntBuffer duplicate ========== 
capacity:	10
limit:	10
position:	0
0	2	0	2	0	3	0	4	0	5

Nio源码地址​github.com