cannot convert from double to float

Question

In my database, I have a couple of "real" fields.

Heres the structure:

    database.execSQL("create table " + TABLE_LOGS + " (" 
            + COLUMN_ID + " integer primary key autoincrement," 
            + COLUMN_ID_DAY_EXERCISE + " integer not null,"
            + COLUMN_REPS + " integer not null"
            + COLUMN_WEIGHT + " real not null"
            + COLUMN_1RM + " real not null"
            + COLUMN_DATE + " integer not null"
            + ")");

Now what I am trying to do is calculate 1RM so that I can insert it into the database.

Here is my function so far:

public void createLog(long id_day_exercise, float reps, long weight) {

    // create 1rm
    // create date timestamp

    float onerm = weight/(1.0278-(.0278*reps));
    long unixTime = System.currentTimeMillis() / 1000L;
}

I am stuck here. It is giving me the error "cannot convert from double to float" for onerm. I've tried casting the weight as a float by using (Float) in front of it, I've tried using weight.floatValue() and nothing seems to work.

Answer 1

Have you tried this?

float onerm = (float) (weigth/(1.0278-(.0278*reps)));

Answer 2

What about this approach?

Float.valueOf(String.valueOf(your_double_variable));

Answer 3

Casting from a double to a float can be done like this:

double d = 1.2;
float f = (float) d;

Or if you just need to express 1.2 as a float to start with, then use 1.2f.

Note

• float is single-precision 32-bit and double is double-precision 64-bit so it is possible to lose precision in the conversion. See the primitive data types documentation.

Answer 4

In my case you have a Double variable, you can call Double.floatValue() like this:

Double deg = 45.0d;
float floatDeg = deg.floatValue();

Answer 5

The issue is that the double type is higher precision than float. You'll lose information when you make that assignment. That's why the compiler doesn't let you do that. It's similar to what happens when you want to do char b = a where a is an int.

Using an explicit cast might allow you to compile, but data/precision loss could happen.

EDIT:

Since in your original question all the inputs to the calculation are floats, use float literals. For example, 1.0278 is a double literal. I.e. append f to the constants such that all the calculations are floats and are not promoted to doubles:

float onerm = weight/(1.0278f-(.0278f*reps));