Java Primitive Data Types -Integers
Each Java data type for representing integers is signed: left most bit 0 means positive, left most bit 1 means negative. The following table describes the integer data types:
|
Primitive data type |
Memory allocation |
Min / Max value |
|
byte |
1 byte |
-128 / 127 |
|
short |
2 bytes |
-32,768 / 32,767 |
|
int |
4 bytes |
-2,147,483,648 / 2,147,483,647 |
|
long |
8 bytes |
-9,223,372,036,854,775,808 / 9,223,372,036,854,775,807 |
Twos complement is the standard convention used to represent signed binary numbers. This avoids having +0 and -0 values, which could complicate hardware requirements. To represent a number in twos complement first note that all positive numbers have a 0 as the left most bit. Inverting all bits in the positive number and adding 1 derives a negative number. Consider the table below which shows the binary representation of Java byte data type (spaces added to binary numbers to improve readability):
|
Java Byte
Data Type |
||||
|
Decimal |
8 bit Binary |
invert |
add 1 for Twos Complement |
Decimal |
|
0 |
0000 0000 |
- |
- |
- |
|
+1 |
0000 0001 |
1111 1110 |
1111 1111 |
-1 |
|
+2 |
0000 0010 |
1111 1101 |
1111 1110 |
-2 |
|
+3 |
0000 0011 |
1111 1100 |
1111 1101 |
-3 |
|
+4 |
0000 0100 |
1111 1011 |
1111 1100 |
-4 |
|
+5 |
0000 0101 |
1111 1010 |
1111 1011 |
-5 |
|
¯ |
|
|
|
¯ |
|
124 |
0111 1100 |
1000 0011 |
1000 0100 |
-124 |
|
125 |
0111 1101 |
1000 0010 |
1000 0011 |
-125 |
|
126 |
0111 1110 |
1000 0001 |
1000 0010 |
-126 |
|
127 |
0111 1111 |
1000 0000 |
1000 0001 |
-127 |
|
- |
- |
- |
1000 0000 |
-128 |
