使用不同的数据类型

Question

public class UnIntentionalObjectCreation {

  private static Byte sumOfIntegerUptoN(Byte N) {
    Byte sum = 0;
    for (Byte i = 0; i < N; i++) {
        sum += i;
    }
    System.out.println(sum);
    return sum;
  }

  public static void main(String[] args) {
    long start = System.currentTimeMillis();
    sumOfIntegerUptoN(10);
    long end = System.currentTimeMillis();
    System.out.println((end - start));

  }
}

Error in 6 line :- Inconvertible type found Error in 14 line:- UnIntentionalObjectCreation cannot be applined to (int)

Answer 1

So your method accepts a Byte , while you are passing an int . You can simply replace Byte variables/methods with int .

public class UnIntentionalObjectCreation {

  private static int sumOfIntegerUptoN(int N) {
    int sum = 0;
    for (int i = 0; i < N; i++) {
        sum += i;
    }
    System.out.println(sum);
    return sum;
  }

  public static void main(String[] args) {
    long start = System.currentTimeMillis();
    sumOfIntegerUptoN(10);
    long end = System.currentTimeMillis();
    System.out.println((end - start));

  }
}

Should do the work.

Answer 2

Byte is an object but his behaviour is different form Integer , Long and Double , you cannot use it for basic arithmetic operations. And even if you can assign an integer number to a Byte object like this:

Byte a = 10;

Quite strangely, you cannot pass an integer number as parameter like you did calling sumOfIntegerUptoN method.

In your case, instead of a Byte I suggest to use a primitive data type like an int .

Byte object is immutable, so you cannot increment and decrement it.

The Byte class wraps a value of primitive type byte in an object. An object of type Byte contains a single field whose type is byte.

You should have a look at what is autoboxing and autounboxing in Java and which kind of primitive data type exists in java .

There is also another aspect I suggest to take care, a Byte is only 8 bit, so the range of number your can handle is quite small (-128/+127).

Answer 3

There are few things I could notice -

One

sumOfIntegerUptoN(10); // this is expected to be of Type

which can be modified as -

sumOfIntegerUptoN(((Integer)10).byteValue()); // wraps the integer converted to byte into Byte

Two

sum += i; //where both these are Byte

the operation is not permitted according to the doc here . Since the values of the variables in the expression above are not known at the compile time.

As it happens in your case, do take a look at Why can not I add two bytes and get an int and I can add two final bytes get a byte?

Hence would recommend changing all the Byte occurrences in your code to int and perform operations accordingly.