Java 基礎 byte[]與各種資料類型互相轉換的簡單範例

Java 基礎byte[]與各種資料型別互相轉換的簡單範例

這裡對byte[]型別對long,int,double,float，short,cahr，object,string型別互相轉換的實例，

在socket在開發過程中，通常需要將一些具體的值（這些值可能是各種Java類型）轉換為byte[]類型，為此我總結瞭如下這個示例，貼出來，以便經常翻看：

public class TestCase { 
    
  /** 
   * short到字节数组的转换. 
   */
  public static byte[] shortToByte(short number) { 
    int temp = number; 
    byte[] b = new byte[2]; 
    for (int i = 0; i < b.length; i++) { 
      b[i] = new Integer(temp & 0xff).byteValue();// 将最低位保存在最低位 
      temp = temp >> 8;// 向右移8位 
    } 
    return b; 
  } 
  
  /** 
   * 字节数组到short的转换. 
   */
  public static short byteToShort(byte[] b) { 
    short s = 0; 
    short s0 = (short) (b[0] & 0xff);// 最低位 
    short s1 = (short) (b[1] & 0xff); 
    s1 <<= 8; 
    s = (short) (s0 | s1); 
    return s; 
  } 
    
    
  /** 
   * int到字节数组的转换. 
   */
  public static byte[] intToByte(int number) { 
    int temp = number; 
    byte[] b = new byte[4]; 
    for (int i = 0; i < b.length; i++) { 
      b[i] = new Integer(temp & 0xff).byteValue();// 将最低位保存在最低位 
      temp = temp >> 8;// 向右移8位 
    } 
    return b; 
  } 
  
  /** 
   * 字节数组到int的转换. 
   */
  public static int byteToInt(byte[] b) { 
    int s = 0; 
    int s0 = b[0] & 0xff;// 最低位 
    int s1 = b[1] & 0xff; 
    int s2 = b[2] & 0xff; 
    int s3 = b[3] & 0xff; 
    s3 <<= 24; 
    s2 <<= 16; 
    s1 <<= 8; 
    s = s0 | s1 | s2 | s3; 
    return s; 
  } 
    
    
  /** 
   * long类型转成byte数组 
   */
  public static byte[] longToByte(long number) { 
    long temp = number; 
    byte[] b = new byte[8]; 
    for (int i = 0; i < b.length; i++) { 
      b[i] = new Long(temp & 0xff).byteValue();// 将最低位保存在最低位 temp = temp 
                            // >> 8;// 向右移8位 
    } 
    return b; 
  } 
  
  /** 
   * 字节数组到long的转换. 
   */
  public static long byteToLong(byte[] b) { 
    long s = 0; 
    long s0 = b[0] & 0xff;// 最低位 
    long s1 = b[1] & 0xff; 
    long s2 = b[2] & 0xff; 
    long s3 = b[3] & 0xff; 
    long s4 = b[4] & 0xff;// 最低位 
    long s5 = b[5] & 0xff; 
    long s6 = b[6] & 0xff; 
    long s7 = b[7] & 0xff; 
  
    // s0不变 
    s1 <<= 8; 
    s2 <<= 16; 
    s3 <<= 24; 
    s4 <<= 8 * 4; 
    s5 <<= 8 * 5; 
    s6 <<= 8 * 6; 
    s7 <<= 8 * 7; 
    s = s0 | s1 | s2 | s3 | s4 | s5 | s6 | s7; 
    return s; 
  } 
    
  /** 
   * double到字节数组的转换. 
   */
  public static byte[] doubleToByte(double num) {  
    byte[] b = new byte[8];  
    long l = Double.doubleToLongBits(num);  
    for (int i = 0; i < 8; i++) {  
      b[i] = new Long(l).byteValue();  
      l = l >> 8;  
    } 
    return b; 
  } 
    
  /** 
   * 字节数组到double的转换. 
   */
  public static double getDouble(byte[] b) {  
    long m;  
    m = b[0];  
    m &= 0xff;  
    m |= ((long) b[1] << 8);  
    m &= 0xffff;  
    m |= ((long) b[2] << 16);  
    m &= 0xffffff;  
    m |= ((long) b[3] << 24);  
    m &= 0xffffffffl;  
    m |= ((long) b[4] << 32);  
    m &= 0xffffffffffl;  
    m |= ((long) b[5] << 40);  
    m &= 0xffffffffffffl;  
    m |= ((long) b[6] << 48);  
    m &= 0xffffffffffffffl;  
    m |= ((long) b[7] << 56);  
    return Double.longBitsToDouble(m);  
  } 
    
    
  /** 
   * float到字节数组的转换. 
   */
  public static void floatToByte(float x) { 
    //先用 Float.floatToIntBits(f)转换成int 
  } 
    
  /** 
   * 字节数组到float的转换. 
   */
  public static float getFloat(byte[] b) {  
    // 4 bytes  
    int accum = 0;  
    for ( int shiftBy = 0; shiftBy < 4; shiftBy++ ) {  
        accum |= (b[shiftBy] & 0xff) << shiftBy * 8;  
    }  
    return Float.intBitsToFloat(accum);  
  }  
  
   /** 
   * char到字节数组的转换. 
   */
   public static byte[] charToByte(char c){ 
    byte[] b = new byte[2]; 
    b[0] = (byte) ((c & 0xFF00) >> 8); 
    b[1] = (byte) (c & 0xFF); 
    return b; 
   } 
     
   /** 
   * 字节数组到char的转换. 
   */
   public static char byteToChar(byte[] b){ 
    char c = (char) (((b[0] & 0xFF) << 8) | (b[1] & 0xFF)); 
    return c; 
   } 
    
  /** 
   * string到字节数组的转换. 
   */
  public static byte[] stringToByte(String str) throws UnsupportedEncodingException{ 
    return str.getBytes("GBK"); 
  } 
    
  /** 
   * 字节数组到String的转换. 
   */
  public static String bytesToString(byte[] str) { 
    String keyword = null; 
    try { 
      keyword = new String(str,"GBK"); 
    } catch (UnsupportedEncodingException e) { 
      e.printStackTrace(); 
    } 
    return keyword; 
  } 
    
    
  /** 
   * object到字节数组的转换 
   */
  @Test
  public void testObject2ByteArray() throws IOException, 
      ClassNotFoundException { 
    // Object obj = ""; 
    Integer[] obj = { 1, 3, 4 }; 
  
    // // object to bytearray 
    ByteArrayOutputStream bo = new ByteArrayOutputStream(); 
    ObjectOutputStream oo = new ObjectOutputStream(bo); 
    oo.writeObject(obj); 
    byte[] bytes = bo.toByteArray(); 
    bo.close(); 
    oo.close(); 
    System.out.println(Arrays.toString(bytes)); 
  
    Integer[] intArr = (Integer[]) testByteArray2Object(bytes); 
    System.out.println(Arrays.asList(intArr)); 
  
  
    byte[] b2 = intToByte(123); 
    System.out.println(Arrays.toString(b2)); 
  
    int a = byteToInt(b2); 
    System.out.println(a); 
  
  } 
  
  /** 
   * 字节数组到object的转换. 
   */
  private Object testByteArray2Object(byte[] bytes) throws IOException, 
      ClassNotFoundException { 
    // byte[] bytes = null; 
    Object obj; 
    // bytearray to object 
    ByteArrayInputStream bi = new ByteArrayInputStream(bytes); 
    ObjectInputStream oi = new ObjectInputStream(bi); 
    obj = oi.readObject(); 
    bi.close(); 
    oi.close(); 
    System.out.println(obj); 
    return obj; 
  } 
  
}

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