在 Java 中不断收到“可能的从 double 到 int 的有损转换”错误

Question

public static int calcCarbonFootprint ( double[] person ) {

    double kgCO2;
    double metricTons;
    kgCO2 = (double)(calcTransit(person[3]));
    kgCO2 += (double)calcAutoOwnership(person[2]);
    kgCO2 += (double)calcAutoUsage(person[0],person[1]);
    metricTons = kgCO2/KGS_PER_METRIC_TON;

    return (int)metricTons;
}

This is the function I'm trying to add, but I keep getting these errors:

./CarbonCalculator.java:142: error: incompatible types: possible lossy conversion from double to int
    kgCO2 = (double)(calcTransit(person[3]));
                                       ^
./CarbonCalculator.java:143: error: incompatible types: possible lossy conversion from double to int
    kgCO2 += (double)calcAutoOwnership(person[2]);
                                             ^
./CarbonCalculator.java:144: error: incompatible types: possible lossy conversion from double to int
    kgCO2 += (double)calcAutoUsage(person[0],person[1]);
                                                   ^

I've tried many different approaches, but all end up in the same error. Could I get some direction?

Answer 1

The error is caused by attempting to pass a double number, which has 64-bits, to an int argument, that has 32 bits.

You can change the parameters of your calc* methods to accept double instead of int . This way the calculation will be as precise as possible.

... or you can cast person[n] to int . Some numerical data from the double type number will disappear, along with the accuracy of the calculation methods.

Example code: https://ideone.com/ghgRo9