Converting from byte to int in java

Question

I have generated a secure random number  and put its value into a byte  Here is my code   SecureRandom ranGen   new SecureRandom    byte   rno   new byte 4    ranGen nextBytes rno   int i   rno 0  intValue      But I am getting an error     byte cannot be dereferenced

User · Answer

Primitive data types  such as byte  don t have methods in java  but you can directly do   int i rno 0

User · Answer

I thought it would be   byte b    byte 255  int i   b  amp 255

User · Answer

byte b    byte 0xC8  int v1   b           v1 is -56  0xFFFFFFC8  int v2   b  amp  0xFF    v2 is 200  0x000000C8    Most of the time v2 is the way you really need

User · Answer

Your array is of byte primitives  but you re trying to call a method on them   You don t need to do anything explicit to convert a byte to an int  just   int i rno 0        since it s not a downcast   Note that the default behavior of byte-to-int conversion is to preserve the sign of the value  remember byte is a signed type in Java   So for instance   byte b1   -100  int i1   b1  System out println i1      -100   If you were thinking of the byte as unsigned  156  rather than signed  -100   as of Java 8 there s Byte toUnsignedInt   byte b2   -100     Or     byte 156   int   Byte toUnsignedInt b2   System out println i2      156   Prior to Java 8  to get the equivalent value in the int you d need to mask off the sign bits   byte b2   -100     Or     byte 156   int i2    b2  amp  0xFF   System out println i2      156     Just for completeness  1  If you did want to use the various methods of Byte for some reason  you don t need to here   you could use a boxing conversion   Byte b   rno 0      Boxing conversion converts  byte  to  Byte  int i   b intValue      Or the Byte constructor   Byte b   new Byte rno 0    int i   b intValue      But again  you don t need that here     Just for completeness  2  If it were a downcast  e g   if you were trying to convert an int to a byte   all you need is a cast   int i  byte b   i   5  b    byte i    This assures the compiler that you know it s a downcast  so you don t get the  Possible loss of precision  error

User · Answer

Bytes are transparently converted to ints   Just say  int i  rno 0

User · Answer

if you want to combine the 4 bytes into a single int you need to do  int i   rno 0  lt  lt 24  amp 0xff000000          rno 1  lt  lt 16  amp 0x00ff0000          rno 2  lt  lt  8  amp 0x0000ff00          rno 3  lt  lt  0  amp 0x000000ff    I use 3 special operators   is the bitwise logical OR  amp  is the logical AND and  lt  lt  is the left shift  in essence I combine the 4 8-bit bytes into a single 32 bit int by shifting the bytes in place and ORing them together   I also ensure any sign promotion won t affect the result with  amp  0xff

[java] Converting from byte to int in java

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