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ByteBuffer

字节缓存区处理子节的，比传统的数组的效率要高。

分类

HeapByteBuffer

用子节数组封装的一种的ByteBuffer,分配在堆上，受GC控制。

DircectByteBuffer

不是分配在堆上，不受GC控制 

两者的区别 1,创建和释放DirectByteBuffer的代价要比HeapByteBuffer要高， 2,DirectByteBuffer的读写的操作要比HeapByteBuffer要快

使用

创建

1.获取HeadByteBuffer

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);

其中ByteBuffer.allocate(20);

public static ByteBuffer allocate(int capacity) {    if (capacity < 0)        throw new IllegalArgumentException();    return new HeapByteBuffer(capacity, capacity);}HeapByteBuffer(int cap, int lim, boolean isReadOnly) {      // package-private    super(-1, 0, lim, cap, new byte[cap], 0);    this.isReadOnly = isReadOnly;}ByteBuffer(int mark, int pos, int lim, int cap, byte[] hb, int offset) {    super(mark, pos, lim, cap, 0);    this.hb = hb;    this.offset = offset;}

新生成了一个长度为capacity的数组，以及一些标示

2.获取DirectByteBuffer对象

ByteBuffer directByteBuffer = ByteBuffer.allocateDirect(20);

其中ByteBuffer.allocateDirect(20);

public static ByteBuffer allocateDirect(int capacity) {    if (capacity < 0) {        throw new IllegalArgumentException("capacity < 0: " + capacity);    }    DirectByteBuffer.MemoryRef memoryRef = new DirectByteBuffer.MemoryRef(capacity);    return new DirectByteBuffer(capacity, memoryRef);}MemoryRef(int capacity) {    VMRuntime runtime = VMRuntime.getRuntime();    buffer = (byte[]) runtime.newNonMovableArray(byte.class, capacity + 7);    allocatedAddress = runtime.addressOf(buffer);    // Offset is set to handle the alignment: http://b/16449607    offset = (int) (((allocatedAddress + 7) & ~(long) 7) - allocatedAddress);    isAccessible = true;}

由runtime去申请了了一块内存。不是直接在堆内存中。

基本操作

再说基本操作之前，先简单说下的ByteBuffer常见的四个标示 

1. position:当前读或者写的位置 2. mark:标记上一次mark的位置，方便reset将postion置为mark的值。 3. limit:标记数据的最大有效的位置 4. capacity:标记buffer的最大可存储值 其中在任意的时候。都必须满足 mark<=position<=limit<=capacity 这里以HeapByteBuffer为例 1.put() position+1,mark不变,limit 不变，capacity不变

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField(heapByteBuffer);for (int i = 0; i < 10; i++) {    heapByteBuffer.put((byte) i);}printField(heapByteBuffer);

打印的结果

capacity: 20 ,limit: 20 ,position: 0 ,mark: -1capacity: 20 ,limit: 20 ,position: 10 ,mark: -1

源码

//putpublic ByteBuffer put(byte x) {    if (isReadOnly) {        throw new ReadOnlyBufferException();    }    hb[ix(nextPutIndex())] = x;    return this;}//nextPutIndexfinal int nextPutIndex(){    if(position>=limit){        throw new BufferOverflowException();    }    return position++;}

2.get() 

position++,mark不变，limit不变，capacity不变

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField(heapByteBuffer);for (int i = 0; i < 10; i++) {
       System.out.print(heapByteBuffer.get());}System.out.println();printField(heapByteBuffer);

打印结果

capacity: 20 ,limit: 20 ,position: 0 ,mark: -10000000000capacity: 20 ,limit: 20 ,position: 10 ,mark: -1

解释下，初始化，该数组的默认值为0，每次调用get的方法，position+1 

源码

public byte get() {    return hb[ix(nextGetIndex())];}

3.filp() 

limit=position,position=0,capacity不变，mark=-1 模拟一次读写

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);//写数据for (int i = 0; i < 10; i++) {    heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.flip();printField("after flip", heapByteBuffer);//读数据for (int i = 0; i < 10; i++) {    System.out.print(heapByteBuffer.get());}System.out.println();printField("after get", heapByteBuffer);

打印的结果

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after flip  capacity: 20 ,limit: 10 ,position: 0 ,mark: -10123456789after get  capacity: 20 ,limit: 10 ,position: 10 ,mark: -1

源码

public final Buffer flip() {    limit = position;    position = 0;    mark = -1;    return this;}

4.rewind 

position=0,mark =-1,limit 不变，capacity不变

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);//写操作for (int i = 0; i < 10; i++) {    heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.rewind();printField("after rewind", heapByteBuffer);//读操作for (int i = 0; i < 10; i++) {    System.out.print(heapByteBuffer.get());}System.out.println();printField("after get", heapByteBuffer);

打印

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after rewind  capacity: 20 ,limit: 20 ,position: 0 ,mark: -10123456789after get  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1

乍一看似乎和flip的没什么区别。但是我们最大ByteBuffer有效数据是到limit的截止的，这也意味着如果在读写切换操作的时候，你使用rewind的时候，会将一部分脏数据读出来。例如下面的�例子

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);//写操作for (int i = 0; i < 10; i++) {    heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.rewind();printField("after rewind", heapByteBuffer);//读操作for (int i = 0; i < heapByteBuffer.limit(); i++) {    System.out.print(heapByteBuffer.get());}System.out.println();printField("after get", heapByteBuffer);

打印的结果

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after rewind  capacity: 20 ,limit: 20 ,position: 0 ,mark: -101234567890000000000after get  capacity: 20 ,limit: 20 ,position: 20 ,mark: -1

我们会面发现后面10个0并不是我们实现写进去的，但是读的时候却读出来了，如果我们使用flip的操作的时候

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);//写数据for (int i = 0; i < 10; i++) {    heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.flip();printField("after flip", heapByteBuffer);//读数据for (int i = 0; i < heapByteBuffer.limit(); i++) {    System.out.print(heapByteBuffer.get());}System.out.println();printField("after get", heapByteBuffer);

打印的结果为

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after flip  capacity: 20 ,limit: 10 ,position: 0 ,mark: -10123456789after get  capacity: 20 ,limit: 10 ,position: 10 ,mark: -1

源码

public final Buffer rewind() {    position = 0;    mark = -1;    return this;}

5.clear() 

position=0,mark =-1,capacity不变,limit=capacity

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);for (int i = 0; i < 10; i++) {
       heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.flip();printField("after flip", heapByteBuffer);for (int i = 0; i < heapByteBuffer.limit(); i++) {
       System.out.print(heapByteBuffer.get());}System.out.println();printField("after get", heapByteBuffer);heapByteBuffer.clear();printField("after clear",heapByteBuffer);for (int i = 0; i < heapByteBuffer.limit(); i++) {
       System.out.print(heapByteBuffer.get());}System.out.println();printField("after get",heapByteBuffer);

打印的结果

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after flip  capacity: 20 ,limit: 10 ,position: 0 ,mark: -10123456789after get  capacity: 20 ,limit: 10 ,position: 10 ,mark: -1after clear  capacity: 20 ,limit: 20 ,position: 0 ,mark: -101234567890000000000after get  capacity: 20 ,limit: 20 ,position: 20 ,mark: -1

可以看到并没有影响buffer的数据 

源码

public final Buffer clear() {    position = 0;    limit = capacity;    mark = -1;    return this;}

6.mark() 

7.reset() mark():mark = position reset():position = mark;

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);for (int i = 0; i < 10; i++) {
       heapByteBuffer.put((byte) i);}printField("after put", heapByteBuffer);heapByteBuffer.mark();printField("after mark", heapByteBuffer);heapByteBuffer.position(15);printField("after position", heapByteBuffer);heapByteBuffer.reset();printField("after reset", heapByteBuffer);

打印的结果

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after put  capacity: 20 ,limit: 20 ,position: 10 ,mark: -1after mark  capacity: 20 ,limit: 20 ,position: 10 ,mark: 10after position  capacity: 20 ,limit: 20 ,position: 15 ,mark: 10after reset  capacity: 20 ,limit: 20 ,position: 10 ,mark: 10

源码

//markpublic final Buffer mark() {    mark = position;    return this;}//resetpublic final Buffer reset() {    int m = mark;    if (m < 0)        throw new InvalidMarkException();    position = m;    return this;}

8.position(int newPosition); 

9.limit(int newLimit); postion(int newPosition):position = newPosition limit(int newLimit):limit = newLimit;

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);heapByteBuffer.position(1);printField("after position", heapByteBuffer);heapByteBuffer.limit(10);printField("after limit", heapByteBuffer);

打印的log

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after position  capacity: 20 ,limit: 20 ,position: 1 ,mark: -1after limit  capacity: 20 ,limit: 10 ,position: 1 ,mark: -1

源码

//position(int newPosition)public final Buffer position(int newPosition) {    if ((newPosition > limit) || (newPosition < 0))        throw new IllegalArgumentException("Bad position " + newPosition + "/" + limit);    position = newPosition;    if (mark > position) mark = -1;    return this;}//limit(int newLimit)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;}

10,remaining 

11,hasRemaining remaining:返回剩余的个数 hasRemaining:返回是否还有剩余

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);printField("after create", heapByteBuffer);System.out.println("remaining:"+heapByteBuffer.remaining());System.out.println("hasRemaining:"+heapByteBuffer.hasRemaining());

打印的log

after create  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1remaining:20hasRemaining:true

源码

//remainingpublic final int remaining() {    return limit - position;}//hasRemainingpublic final boolean hasRemaining() {    return position < limit;}

12,wrap(byte[] byte) 

byte变成ByteBuffer: 共用一套的数据，相当于allocate and put,不影响标记量

ByteBuffer wrapByteBuffer = ByteBuffer.wrap(new byte[10]);printField("after",wrapByteBuffer);

打印log

after  capacity: 10 ,limit: 10 ,position: 0 ,mark: -1

源码

public static ByteBuffer wrap(byte[] array) {    return wrap(array, 0, array.length);}//return HeapByteBufferpublic static ByteBuffer wrap(byte[] array,int offset, int length) {    try {        return new HeapByteBuffer(array, offset, length);    } catch (IllegalArgumentException x) {        throw new IndexOutOfBoundsException();    }}//array = hbByteBuffer(int mark, int pos, int lim, int cap, byte[] hb, int offset) {    super(mark, pos, lim, cap, 0);    this.hb = hb;    this.offset = offset;}

13,put(byte[] byte),将byte的数组放进bytebuffer，相当于byte.length次数往bytebuffer添加byte[index],影响position的位置。

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);byte[] buffer = new byte[]{        1, 2, 3, 4, 6, 7, 8, 9    };heapByteBuffer.put(buffer);printField("after put",heapByteBuffer);

打印的log

after put  capacity: 20 ,limit: 20 ,position: 8 ,mark: -1

源码

public final ByteBuffer put(byte[] src) {    return put(src, 0, src.length);}public ByteBuffer put(byte[] src, int offset, int length) {    checkBounds(offset, length, src.length);    if (length > remaining())        throw new BufferOverflowException();    int end = offset + length;    for (int i = offset; i < end; i++)        this.put(src[i]);    return this;}

14,get(byte[] byte) 

取数据，放入到byte数组里面,数组之间不影响，相当于多次的get的操作,影响的position的位置。

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);byte[] buffer = new byte[]{    1, 2, 3, 4, 6, 7, 8, 9};heapByteBuffer.put(buffer);printField("after put", heapByteBuffer);heapByteBuffer.rewind();printField("after rewind", heapByteBuffer);byte[] outBuffer = new byte[20];heapByteBuffer.get(outBuffer);printField("after get", heapByteBuffer);for(int i = 0;i < outBuffer.length;i++){    System.out.print(outBuffer[i]);}

打印的log

after put  capacity: 20 ,limit: 20 ,position: 8 ,mark: -1after rewind  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after get  capacity: 20 ,limit: 20 ,position: 20 ,mark: -112346789000000000000

源码

public ByteBuffer get(byte[] dst) {    return get(dst, 0, dst.length);}public ByteBuffer get(byte[] dst, int offset, int length) {    checkBounds(offset, length, dst.length);    if (length > remaining())        throw new BufferUnderflowException();    int end = offset + length;    for (int i = offset; i < end; i++)        dst[i] = get();    return this;}

15,put(int index,byte b) 

16,get(int index) 去或者放index位置的值,注意此时不影响position的位置

ByteBuffer heapByteBuffer = ByteBuffer.allocate(20);heapByteBuffer.put(2, (byte) 2);printField("after put(index):", heapByteBuffer);System.out.print(heapByteBuffer.get(2));printField("after get(index):", heapByteBuffer);

打印的log

after put(index):  capacity: 20 ,limit: 20 ,position: 0 ,mark: -12after get(index):  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1

源码分析

//put(int index, byte b);public ByteBuffer put(int i, byte x) {    if (isReadOnly) {        throw new ReadOnlyBufferException();    }    //checkIndex() not nextIndex    hb[ix(checkIndex(i))] = x;    return this;}//get(int index)public byte get(int i) {    //chekIndex not nextIndex    return hb[ix(checkIndex(i))];}

17,slice 

复制有限区域段的byteBuffer,即position到limit的位置。返回的ByteBuffer的position=1,mark=-1,limit=capaticy =src.remaining,并且两个byteBuffer里面的数组相互影响

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});printField("after warp", heapByteBuffer);//mark = 0heapByteBuffer.mark();//position = 5;heapByteBuffer.position(5);//limit = 15;heapByteBuffer.limit(15);ByteBuffer slice = heapByteBuffer.slice();printField("after slice", slice);for (int i = 0; i < slice.limit(); i++) {
       System.out.print(slice.get());}System.out.println();//index = 7,value = 31;slice.put(7, (byte) 31);System.out.println(slice.get(7));System.out.println(heapByteBuffer.get(12));

打印的log

after warp  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1after slice  capacity: 10 ,limit: 10 ,position: 0 ,mark: -15678910111213143131

源码分析

public ByteBuffer slice() {    return new HeapByteBuffer(hb,        -1,        0,        remaining(),        remaining(),        position() + offset,        isReadOnly);}//-1 = mark 0 = position//limit = capitity = remaining()//offset = position()+offsetprotected HeapByteBuffer(byte[] buf,int mark, int pos, int lim, int cap,int off, boolean isReadOnly) {    super(mark, pos, lim, cap, buf, off);    this.isReadOnly = isReadOnly;}

18,duplicate 

复制的操作，包括所有的标示浮，并且两个ByteBuffer的内存的数组是共同的。

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});printField("after warp", heapByteBuffer);//mark = 0heapByteBuffer.mark();//position = 5;heapByteBuffer.position(5);//limit = 15;heapByteBuffer.limit(15);ByteBuffer duplicate = heapByteBuffer.duplicate();printField("heapByteBuffer", heapByteBuffer);printField("duplicate", duplicate);duplicate.rewind();for (int i = 0; i < duplicate.limit(); i++) {
       System.out.print(duplicate.get());}System.out.println();//index = 7,value = 31;duplicate.put(7, (byte) 31);System.out.println(duplicate.get(7));System.out.println(heapByteBuffer.get(7));

打印的log

after warp  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1heapByteBuffer  capacity: 20 ,limit: 15 ,position: 5 ,mark: 0duplicate  capacity: 20 ,limit: 15 ,position: 5 ,mark: 0012345678910111213143131

源码分析

//mark = markValue,position= position//limit = limit(),capacity= capacity()public ByteBuffer duplicate() {    return new HeapByteBuffer(hb,        markValue(),        position(),        limit(),        capacity(),        offset,        isReadOnly);}

19,array 

将ByteBuffer转成一个数组，相比get(byte[]b)而言，这两个数组相互影响，但不影响position 的位置。

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});printField("after warp", heapByteBuffer);//mark = 0heapByteBuffer.mark();//position = 5;heapByteBuffer.position(5);//limit = 15;heapByteBuffer.limit(15);byte[] array = heapByteBuffer.array();printField("heapByteBuffer", heapByteBuffer);for (int i = 0; i < array.length; i++) {    System.out.print(array[i]);}System.out.println();//index = 7,value = 31;array[7] = 31;System.out.println(array[7]);System.out.println(heapByteBuffer.get(7));

打印的log

after warp  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1heapByteBuffer  capacity: 20 ,limit: 15 ,position: 5 ,mark: 00123456789101112131415161718193131

源码分析

public final byte[] array() {    if (hb == null)        throw new UnsupportedOperationException();    if (isReadOnly)        throw new ReadOnlyBufferException();    return hb;}

20,compact 

将positon到limit的内容复制到0~(limit-position)的位置上，并且pisition=limit-position,limit = capatity()

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});printField("after warp", heapByteBuffer);//mark = 0heapByteBuffer.mark();//position = 5;heapByteBuffer.position(5);//limit = 15;heapByteBuffer.limit(15);ByteBuffer compact = heapByteBuffer.compact();printField("heapByteBuffer", heapByteBuffer);heapByteBuffer.rewind();for (int i = 0; i < heapByteBuffer.limit(); i++) {    System.out.print(heapByteBuffer.get());}

打印的log

after warp  capacity: 20 ,limit: 20 ,position: 0 ,mark: -1heapByteBuffer  capacity: 20 ,limit: 20 ,position: 10 ,mark: -156789101112131410111213141516171819

源码分析

public ByteBuffer compact() {    if (isReadOnly) {        throw new ReadOnlyBufferException();    }    // 从position开始复制到remaining位置    System.arraycopy(hb, ix(position()), hb, ix(0), remaining());    //postion=remaining();    position(remaining());    //limit=capacity()    limit(capacity());    discardMark();    return this;    }

21.order 

22.getInt()/getLong()等 内存中的数据有高序和低序之分的，那么不同的排序，输出的结果也是不同的，同样ByteBuffer中的字节也是有排序的，简称大端和小端排序，通过order来控制数据排序。 我们知道byte占一个子节，int占4个子节，那么就意味着，如果getInt(),则需要byteBuffer中一次取4个子节。这样就能保证取出的是int的数值，

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});heapByteBuffer.order();printField("order",heapByteBuffer);System.out.println(heapByteBuffer.getInt());//0123System.out.println(heapByteBuffer.getInt());//4567System.out.println(heapByteBuffer.getInt());//891011System.out.println(heapByteBuffer.getInt());//12131415System.out.println(heapByteBuffer.getInt());//16171819

打印的log

6605167438087134810123202182159269554195

解释下： 

66051 = 0*256*256*256+1*256*256+2*256+3 //0123 67438087 = 4*256*256*256+5*256*256+6*256+7 //4567 134810123 = 8*256*256*256+9*256*256+10*256+11 //891011 …

如果将order的顺序改成ByteOrder.LITTLE_ENDIAN 

代码如下

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});heapByteBuffer.order(ByteOrder.LITTLE_ENDIAN);printField("order",heapByteBuffer);System.out.println(heapByteBuffer.getInt());//3210System.out.println(heapByteBuffer.getInt());//7654System.out.println(heapByteBuffer.getInt());//111098System.out.println(heapByteBuffer.getInt());//15141312System.out.println(heapByteBuffer.getInt());//19181716

打印的log

order  capacity: 20 ,limit: 20 ,position: 0 ,mark: -150462976117835012185207048252579084319951120

解释下： 

50462976 = 3*256*256*256+2*256*256+1*256+0;//3210 117835012 = 7*256*256*256+6*256*256+5*256+4;//7654 … 源码的分析

public int getInt() {    //position+4    return Bits.getInt(this, ix(nextGetIndex(4)), bigEndian);}

23,asInterBuffer/asLongBuffer 

转化成IntBuffer或者其他基本数据的Buffer，并且共享一块数组区域

ByteBuffer heapByteBuffer = ByteBuffer.wrap(new byte[]{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19});IntBuffer intBuffer = heapByteBuffer.asIntBuffer();printField("intBuffer", heapByteBuffer);for (int i = 0; i < intBuffer.limit(); i++) {    System.out.println(intBuffer.get());}intBuffer.put(0,256);for(int i = 0;i < heapByteBuffer.limit();i++){    System.out.print(heapByteBuffer.get());

打印的log

intBuffer  capacity: 20 ,limit: 20 ,position: 0 ,mark: -16605167438087134810123202182159269554195001045678910111213141516171819

源码分析

public IntBuffer asIntBuffer() {    //size/4    int size = this.remaining() >> 2;    int off = position();    //ByteBufferAsIntBuffer 是InterBuffer    return (IntBuffer) (new ByteBufferAsIntBuffer(this,        -1,        0,        size,        size,        off,        order()));}

和其他的类常见操作

1,File 

创建一个FileChanel

FileChannel fc = new FileInputStream().getChannel();

读数据

fc.read(byteBuffer);byteBuffer.flip();

写数据

fc.write(byteBuffer);byteBuffer.clear;fc.close;

简单的例子 copy的操作

File readFile = new File("bytebuffertest/read.txt");File outFile = new File("bytebuffertest/write.txt");try {    FileChannel readChannel = new FileInputStream(readFile).getChannel();    ByteBuffer readBuffer = ByteBuffer.allocate(2);    FileChannel outChannel = new FileOutputStream(outFile).getChannel();    while (readChannel.read(readBuffer) >= 0) {        readBuffer.flip();                System.out.print(Charset.forName("utf-8").decode(readBuffer));        readBuffer.flip();        outChannel.write(readBuffer);        readBuffer.clear();    }} catch (FileNotFoundException e) {    e.printStackTrace();} catch (IOException e) {    e.printStackTrace();}

打印log

hello readi cam come from read.text,want to copy write.txts

同时read.txt的内容转到了write.txt.

2,Socket 

创建一个SocketChanel

SocketChanel socketChanel = socket.getChanel();

写数据

socketChannel.write(buffer);

读数据

int bytesReaded=socketChannel.read(buffer);

这里就不举例子了。

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