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javaoverflowunderflow

Overflow and Underflow in Java Float and Double Data Types

I have created the following code to test Float and Double Java numeric data types for underflow and overflow:

// Float Overflow & Underflow
float floatTest = Float.MAX_VALUE;
floatTest++;
out.println("Float Overflow: " + Float.MAX_VALUE + " + 1 = " + floatTest);
floatTest = Float.MIN_VALUE;
floatTest--;
out.println("Float Underflow: " + Float.MIN_VALUE + " - 1 = " + floatTest);
out.println("");

// Double Overflow & Underflow
double doubleTest = Double.MAX_VALUE;
doubleTest++;
out.println("Double Overflow: " + Double.MAX_VALUE + " + 1 = " + doubleTest);
doubleTest = Double.MIN_VALUE;
doubleTest--;
out.println("Double Underflow: " + Double.MIN_VALUE + " - 1 = " + doubleTest);
out.println("");

Can someone explain the weird values I see in the result: enter image description here

When I do the similar test (code below) with byte, short, int and long:

// BYTE Overflow & Underflow
byte byteTest = Byte.MAX_VALUE;
byteTest++;
out.println("Byte Overflow: " + Byte.MAX_VALUE + " + 1 = " + byteTest);
byteTest = Byte.MIN_VALUE;
byteTest--;
out.println("Byte Underflow: " + Byte.MIN_VALUE + " - 1 = " + byteTest);
out.println("");

// SHORT Overflow & Underflow
short shortTest = Short.MAX_VALUE;
shortTest++;
out.println("Short Overflow: " + Short.MAX_VALUE + " + 1 = " + shortTest);
shortTest = Short.MIN_VALUE;
shortTest--;
out.println("Short Underflow: " + Short.MIN_VALUE + " - 1 = " + shortTest);
out.println("");

// INTEGER Overflow & Underflow
int intTest = Integer.MAX_VALUE;
intTest++;
out.println("Integer Overflow: " + Integer.MAX_VALUE + " + 1 = " + intTest);
intTest = Integer.MIN_VALUE;
intTest--;
out.println("Integer Underflow: " + Integer.MIN_VALUE + " - 1 = " + intTest);
out.println("");

// LONG Overflow & Underflow
long longTest = Long.MAX_VALUE;
longTest++;
out.println("Long Overflow: " + Long.MAX_VALUE + " + 1 = " + longTest);
longTest = Long.MIN_VALUE;
longTest--;
out.println("Long Underflow: " + Long.MIN_VALUE + " - 1 = " + longTest);
out.println("");

The results look as expected:

enter image description here

Can someone explain overflow and underflow in Java float and double and why am I seeing above results?

Solution

  • These "weird" results are not really specific to Java. It's just that floats as defined by the relevant IEEE standard, are much more complicated than most people suspect. But onto your specific results: Float.MIN_VALUE is the smallest positive float, so it's very close to 0. Hence Float.MIN_VALUE - 1 will be very close to -1. But since the float precision around -1 is greater than that difference, it comes out as -1. As to Float.MAX_VALUE, the float precision around this value is much greater than 1 and adding one doesn't change the result.