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Program organization
As you can see from Listing 1 , this program contains two class definitions:
As explained above, all of the source code is contained in a single disk file named Division01.java .
The class named Division01 is what I will frequently refer to as the driver class. In particular, it contains the main method, where execution begins and ends in a Java application.
A simple main method
In accordance with specification 13 of the course description , the main method is very simple. In particular, the main method instantiates a new object of the class named Worker , and calls a method named doWork belonging to that object. All of the work in the program is performed by the method named doWork .
Back to the question...
Now let's get back to the question that was posed earlier . Which of the outputs listed above are produced by the program code in Listing 1 ?
Explanation
This program illustrates the integer truncation that results when the division operator is applied to operands of the integer types.
The result of simple long division
We all know that when we divide 101 by 3, the result is 33.666666 with the sixes extending out to the limit of our arithmetic accuracy. (Confirm it using your hand calculator.)
The result of rounding
If we round the quotient to the next closest integer, the result is 34.
Integer division does not round
However, when division is performed using operands of integer types in Java, the fractional part is simply discarded (not rounded) . The result is the whole number result without regard for the fractional part or the remainder.Thus, with integer division, 101/3 produces the integer value 33.
If either operand is a floating type...
If either operand is one of the floating types,
And the answer to the question is...
The code in Listing 1 displays 33 on the standard output device (typically the command-line screen) .
Let's continue with another question. What output is produced by the program shown in Listing 2 ?
| Listing 2 . Arithmetic overflow. |
|---|
public class Overflow01{
public static void main(String args[]){
new Worker().doWork();}//end main()
}//end class definitionclass Worker{
public void doWork(){//Integer.MAX_VALUE = 2147483647
int myVar01 = Integer.MAX_VALUE;int myVar02 = 2;
System.out.println(myVar01 + myVar02);}//end doWork()
}//end class definition |
Explanation
This program illustrates a dangerous situation involving arithmetic using operands of integer types. This situation involves a condition commonly known as integer overflow or arithmetic overflow . This problem usually involves either the addition or multiplication of integer operands.
The good news
The good news about doing arithmetic using operands of integer types is that as long as the result is within the allowable value range for the wider of the integer types, the results are exact (floating arithmetic often produces results that are not exact) .
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