java:多字节数据类型数组(double,float,int,long)数组与byte数组的相互转换

多字节数据类型数组(double,float,int,long)数组数组和byte数组的相互转换都可以基于java.nio.Buffer实现.
java.nio.DoubleBuffer对应double[],
java.nio.FloatBuffer对应float[],
java.nio.LongBuffer对应long[],
java.nio.IntBuffer对应int[]
…

byte[] 转 double[],float[],int[]…

byte[]转double[],float[],int[]…很简单因为ByteBuffer本身就有asDoubleBuffer,asFloatBuffer,asIntBuffer等方法，可以将ByteBuffer直接转换为DoubleBuffer,FloatBuffer,IntBuffer…;
代码实现如下:

	public static double[] asDoubleArray(byte[] input){
		if(null == input ){
			return null;
		}
		DoubleBuffer buffer = ByteBuffer.wrap(input).asDoubleBuffer();
		double[] res = new double[buffer.remaining()];
		buffer.get(res);
		return res;
	}
	public static float[] asFloatArray(byte[] input){
		if(null == input ){
			return null;
		}
		FloatBuffer buffer = ByteBuffer.wrap(input).asFloatBuffer();
		float[] res = new float[buffer.remaining()];
		buffer.get(res);
		return res;
	}
	public static int[] asIntArray(byte[] input){
		if(null == input ){
			return null;
		}
		IntBuffer buffer = ByteBuffer.wrap(input).asIntBuffer();
		int[] res = new int[buffer.remaining()];
		buffer.get(res);
		return res;
	}
	public static long[] asLongArray(byte[] input){
		if(null == input ){
			return null;
		}
		LongBuffer buffer = ByteBuffer.wrap(input).asLongBuffer();
		long[] res = new long[buffer.remaining()];
		buffer.get(res);
		return res;
	}
	public static short[] asShortArray(byte[] input){
		if(null == input ){
			return null;
		}
		ShortBuffer buffer = ByteBuffer.wrap(input).asShortBuffer();
		short[] res = new short[buffer.remaining()];
		buffer.get(res);
		return res;
	}

double[],float[],int[]…转byte[]

反过来，从多字节类型数组(double[],float[],long[]…)转byte[]要稍麻烦一些，因为多字节类型数组对应的Buffer类并没提供asByteBuffer这样的方法.所以要自己写些代码进行转换(比如将DoubleBuffer转为ByteBuffer),实现代码如下：

	/** * {@link DoubleBuffer} TO {@link ByteBuffer} * @param input * @return */
	public static ByteBuffer asByteBuffer(DoubleBuffer input){
		if(null == input ){
			return null;
		}
		ByteBuffer buffer = ByteBuffer.allocate(input.capacity()* (Double.SIZE/8));
		while(input.hasRemaining()){
			buffer.putDouble(input.get());
		}
		return buffer;
	}
	/** * double[] TO byte[] * @param input * @return */
	public static byte[] asByteArray(double[] input){
		if(null == input ){
			return null;
		}
		return asByteBuffer(DoubleBuffer.wrap(input)).array();
	}
	/** * {@link FloatBuffer} TO {@link ByteBuffer} * @param input * @return */
	public static ByteBuffer asByteBuffer(FloatBuffer input){
		if(null == input ){
			return null;
		}
		ByteBuffer buffer = ByteBuffer.allocate(input.capacity()* (Float.SIZE/8));
		while(input.hasRemaining()){
			buffer.putFloat(input.get());
		}
		return buffer;
	}
	/** * float[] TO byte[] * @param input * @return */
	public static byte[] asByteArray(float[] input){
		if(null == input ){
			return null;
		}
		return asByteBuffer(FloatBuffer.wrap(input)).array();
	}
	/** * {@link IntBuffer} TO {@link ByteBuffer} * @param input * @return */
	public static ByteBuffer asByteBuffer(IntBuffer input){
		if(null == input ){
			return null;
		}
		ByteBuffer buffer = ByteBuffer.allocate(input.capacity()* (Integer.SIZE/8));
		while(input.hasRemaining()){
			buffer.putInt(input.get());
		}
		return buffer;
	}
	/** * int[] TO byte[] * @param input * @return */
	public static byte[] asByteArray(int[] input){
		if(null == input ){
			return null;
		}
		return asByteBuffer(IntBuffer.wrap(input)).array();
	}
	/** * {@link LongBuffer} TO {@link ByteBuffer} * @param input * @return */
	public static ByteBuffer asByteBuffer(LongBuffer input){
		if(null == input ){
			return null;
		}
		ByteBuffer buffer = ByteBuffer.allocate(input.capacity()* (Long.SIZE/8));
		while(input.hasRemaining()){
			buffer.putLong(input.get());
		}
		return buffer;
	}
	/** * long[] TO byte[] * @param input * @return */
	public static byte[] asByteArray(long[] input){
		if(null == input ){
			return null;
		}
		return asByteBuffer(LongBuffer.wrap(input)).array();
	}
	/** * {@link ShortBuffer} TO {@link ByteBuffer} * @param input * @return */
	public static ByteBuffer asByteBuffer(ShortBuffer input){
		if(null == input ){
			return null;
		}
		ByteBuffer buffer = ByteBuffer.allocate(input.capacity()* (Short.SIZE/8));
		while(input.hasRemaining()){
			buffer.putShort(input.get());
		}
		return buffer;
	}
	/** * short[] TO byte[] * @param input * @return */
	public static byte[] asByteArray(short[] input){
		if(null == input ){
			return null;
		}
		return asByteBuffer(ShortBuffer.wrap(input)).array();
	}