Unsigned int in Java

Java does not have unsigned data types. Your options are:

• Use a long
• Use an UnsignedInteger from Guava
• Use an int and interpret the bits as unsigned (described below)

An unsigned int

An int is always signed in Java, but nothing prevents you from viewing an int simply as 32 bits and interpret those bits as a value between 0 and 2⁶⁴.

Keep in mind that there’s nothing you can do to force your interpretation upon someone else’s method. If a method accepts a int, then that method accepts a value between −2³¹ and 2³¹ − 1 unless explicitly stated otherwise.

Here are a couple of useful conversions / manipulations.

Printing an unsigned int

Use Integer.toUnsignedString:

System.out.println("Value of my unsigned int: " + Integer.toUnsignedString(uint));

Converting from long to unsigned int

Casting to int throws away all but the lowest 32 bits.

long lng = 2200000000L;  // 00000000 ... 00000000 10000011 00100001 01010110 00000000
int i = (int) lng;       //                       10000011 00100001 01010110 00000000

System.out.println(i);                            // -2094967296
System.out.println(Integer.toUnsignedString(i));  // 2200000000

Converting from unsigned int to long

Use Integer.toUnsignedLong to avoid sign extension.

int i = 0b10000011001000010101011000000000;  // -2094967296 or 2200000000

long signed = i;                             // -2094967296 (with sign extension)
long unsigned = Integer.toUnsignedLong(i);   //  2200000000 (without sign extension)

Or, equivalently:

long unsigned = i & 0xffffffffL;

Comparing unsigned ints

int cmp = Integer.compareUnsigned(i1, i2);
// cmp = -1  =>  i1 < i2
// cmp =  0  =>  i1 = i2
// cmp =  1  =>  11 > i2

Parsing an unsigned int

int i = Integer.parseUnsignedInt("2200000000");

System.out.println(Integer.toUnsignedString(i)); // 2200000000

Note: Integer.parseInt would throw a NumberFormatException for the above input.

Arithmetics

As it happens, the 2-complement representation “just works” for addition, subtraction and multiplication.

// two unsigned ints
int i1 = (int) 2200000000L;
int i2 = 55555;

int sum  = i1 + i2;  // 2200055555
int diff = i1 - i2;  // 2199944445
int prod = i2 * i2;  // 3086358025

For division and remainder, use Integer.divideUnsigned and Integer.remainderUnsigned:

int q = Integer.divideUnsigned(i1, i2);     // 39600
int r = Integer.remainderUnsigned(i1, i2);  // 22000