CODEWITHSUNDEEP
javajavascript
Zahid H
Zahid H

Reputation: 245

Converting from JavaScript to Java but not giving same output

I have some lines of code that produces a number after calculation which is currently in JavaScript and here is the code:

if ( y2 != y1 )
{
    // calculate rate
    var f;
    var y;
    if ( y2 > y1 )
    {
        f = cpi[y2] / cpi[y1];
        y = y2 - y1;
    }
    else
    {
        f = cpi[y1] / cpi[y2];
        y = y1 - y2;
    }           
    var r = Math.pow(f, 1/y);
    r = (r-1)*100;
    r = Math.round(r*100) / 100;
    System.out.println( "number: " + r.toFixed(2) + "%." );
}

I converted the above JS code to Java and here is the code:

DecimalFormat decimalFormat = new DecimalFormat("0.##");
    if (cpi[to] != cpi[from]) {
        double f, y;
        if (cpi[to] > cpi[from]) {
            f = cpi[to] / cpi [from];
            y = to - from;
        }
        else {
            f = cpi[from] / cpi[to];
            y = from - to;
        }
        q = Math.pow(f, 1/y);
        q = (q-1)*100;
        q = Math.round(q*100)/100;
        Toast.makeText(getApplicationContext(), "number: " + String.valueOf(decimalFormat.format(q)), 2000).show();
    }

The JavaScript code produces: number: 2.39

While the Java code produces number: 2

Why am I getting two different value? I will post what cpi[to], cpi[from], to and from values are if needed.

Upvotes: 0

Views: 121

Answers (4)

Vae
Vae

Reputation: 60

Most likely your issue is Math.round(double) returns a long value. So d would contain a long instead of a double at that point.

Upvotes: 0

libik
libik

Reputation: 23029

If you devide two integers in java the result is integer. Every operation with double and integer or with two doubles creates double.

1)In this line

1)q = Math.round(q*100)/100;

2)you are deviding two integers, so it has same output as:

2)q = (int) (Math.round(q*100)/100);

3)you can use casting to double for example:

3)q = Math.round(q*100)/(double)100;

4)or using the 100.0 which makes this number double:

4)q = Math.round(q*100)/100.0;

5)this should work too, because first the result of Math.round is converted to double and then devided by 100:

5)q = (double)Math.round(q*100)/100;

6)However this WILL NOT work, because first Math.round is devided by 100 and it creates integer, so the result of this operation is rounded down and AFTER then casted to double. So it will be double but still rounded down, because it was rounded before it becomes double.

6)q = (double)(Math.round(q*100)/100);

Upvotes: 1

X-Pippes
X-Pippes

Reputation: 1170

what is q type? try to put 100.0 also

Upvotes: 1

Marko Topolnik
Marko Topolnik

Reputation: 200158

In this line

q = Math.round(q*100)/100;

both operands of the division operation are integral, therefore the result is also an integral type. Use 100.0 as the divisor to coerce the result to a double.

Upvotes: 2

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