Java Byte-Size Integers

This post checks what you can and cannot store in a Java byte variable. In prog2, I tried to store -129 in a Java byte variable:

UBUNTU > cat prog2.java
public class prog2
{
public static void main (String args[])
  {
  // Declare a byte-size integer:
  byte num1;

  // Check what values it can store:
  num1 = -129;

  // Display the value:
  System.out.println("num1 = " + num1);
  }
}
UBUNTU >

... but I was unable to compile it:

UBUNTU > javac prog2.java
prog2.java:9: possible loss of precision
found   : int
required: byte
  num1 = -129;
          ^
1 error
UBUNTU >

In prog3, I tried to use a Java byte variable to store -128 and this worked:

UBUNTU > cat prog3.java
public class prog3
{
public static void main (String args[])
  {
  // Declare a byte-size integer:
  byte num1;

  // Check what values it can store:
  num1 = -128;

  // Display the value:
  System.out.println("num1 = " + num1);
  }
}
UBUNTU > javac prog3.java
UBUNTU > java prog3
num1 = -128
UBUNTU > 

In prog4, I tried to use a Java byte variable to store 127 and this worked too:

UBUNTU > cat prog4.java
public class prog4
{
public static void main (String args[])
  {
  // Declare a byte-size integer:
  byte num1;

  // Check what values it can store:
  num1 = 127;

  // Display the value:
  System.out.println("num1 = " + num1);
  }
}
UBUNTU > javac prog4.java
UBUNTU > java prog4
num1 = 127
UBUNTU >

In prog5, I tried to store 128 in a Java byte variable but this produced a compilation error:

UBUNTU > cat prog5.java
public class prog5
{
public static void main (String args[])
  {
  // Declare a byte-size integer:
  byte num1;

  // Check what values it can store:
  num1 = 128;

  // Display the value:
  System.out.println("num1 = " + num1);
  }
}
UBUNTU > javac prog5.java
prog5.java:9: possible loss of precision
found   : int
required: byte
  num1 = 128;
         ^
1 error
UBUNTU >

So it seems that Java byte variables can be used to store integers from -128 to +127, both inclusive.

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