CODEWITHSUNDEEP
javastatic-methods
user2967353
user2967353

Reputation: 267

Read variables from static method into main method as argument when calling the method

I am having trouble on fixing my program, In my last two lines of code, when I call the static method for surfaceGravity, the compiler complains about the argument radius with the statement "incompatible: double cannot be converted to a double[]" and when I call the static method for display, the compiler complains about the argument g with the statement "cannot find symbol". How do I fix this? Any help will be greatly appreciated. Below is my code:

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;

public class GravityV1{

// calculate surface gravity static method
public static double[] surfaceGravity(double G, double[] M, double[] r){

    // surface gravity variable
    double[] g = new double[M.length];

    for(int i = 0; i < g.length; i++){

        // equation for calculating surface gravity
        g[i] = (G * M[i]) / Math.pow(r[i], 2);
    }

    // return statement
    return g;
}

// displaying static method

// write results to text file static method
public static String[] writeToFile() throws IOException{

    int index = 0;
    String[] data = new String[index];
    File filename = new File("/Users/timothylee/Gravity1.txt");
    Scanner inFile = new Scanner(filename);
    while(inFile.hasNext()){

        data[index] = inFile.next( );

        index++;

    }

    inFile.close();
    return data;
}

public static void main(String args[]) throws IOException{

    // declare array for months
    String[] Planets = new String[8];

    // initialize array
    Planets [0] = "Mercury";
    Planets [1] = "Venus";
    Planets [2] = "Earth";
    Planets [3] = "Mars";
    Planets [4] = "Jupiter";
    Planets [5] = "Saturn";
    Planets [6] = "Uranus";
    Planets [7] = "Neptune";

    // declare array for mass
    double[] mass = new double[8];

    // initialize array
    mass [0] = 3.30E23;
    mass [1] = 4.869E24;
    mass [2] = 5.97E24;
    mass [3] = 6.4219E23;
    mass [4] = 1.900E27;
    mass [5] = 5.68E26;
    mass [6] = 8.683E25;
    mass [7] = 1.0247E26;

    // declare array for diameter
    double[] diameter = new double[8];

    // initialize array
    diameter [0] = 4880;
    diameter [1] = 12103.6;
    diameter [2] = 12756;
    diameter [3] = 6794;
    diameter [4] = 142984;
    diameter [5] = 120536;
    diameter [6] = 51118;
    diameter [7] = 49532;


    double[] surfaceG = new double[8];
    // // convert to radius

    // declare radius variable
    double radius = 0;

    // for each loop for displaying
    for(double calc : diameter){

        // calculation for converting to radius
        radius =  calc / 2;
    }

    // // calculate surface gravity

    // declare and initialize universal gravity constant;
    double G = 6.67384 * Math.pow(10, -11);

    // call surface gravity method
    surfaceGravity(G, mass, radius);

    // display result
    display(Planets, radius, mass, g);
}
}

Upvotes: 0

Views: 182

Answers (5)

Yiping Wang
Yiping Wang

Reputation: 11

You are trying to convert a double into a double[] variable, which doesn't make sense. 

double[] surfaceGravity(double G, double[] M, double[] r)

in prototype, 'r' is an annary. However, radius in 'surfaceGravity(G, mass, radius);' is double primitive.

Upvotes: 0

Luuk
Luuk

Reputation: 76

In this line:

public static double[] surfaceGravity(double G, double[] M, double[] r){

You declare that r should be of type double array, but in your main method here:

double radius = 0;

You declare radius to be of type double. Clearly these two are incompatible.

Also, in your main method when you call:

surfaceGravity(G, mass, radius);

Which returns a double array, you never assign the return value to anything. You can resolve this by saying:

double[] g = surfaceGravity(G, mass, radius);

Upvotes: 0

Nikoloz
Nikoloz

Reputation: 553

To fix your first problem you should replace your code:

// declare radius variable
double radius = 0;

// for each loop for displaying
for(double calc : diameter){

    // calculation for converting to radius
    radius =  calc / 2;
}

with this:

// declare radius variable
double radius[] = new double[diameter.length];

// for each loop for displaying
for (int i = 0; i < radius.length; i++){

   // calculation for converting to radius
   radius[i] =  diameter[i] / 2;
}

And to fix second problem you should replace:

// call surface gravity method
surfaceGravity(G, mass, radius);

with this:

// call surface gravity method
double[] g = surfaceGravity(G, mass, radius);

Upvotes: 1

Sage
Sage

Reputation: 15418

double[] surfaceGravity(double G, double[] M, double[] r)

you are calling this function with wrong type of parameter:

surfaceGravity(G, mass, radius);

radius is primitive type variable with double. The third parameter to be passed must be an array. So you must pass pass an array in place of radius. Change your method's parameter type:

double[] surfaceGravity(double G, double[] M, double r)

, the compiler complains about the argument g with the statement "cannot find symbol". How do I fix this?

you haven't declared any variable g in your class context or main() function context. So declare it with relevant type and in proper context.

Upvotes: 0

mychalvlcek
mychalvlcek

Reputation: 4046

as the compiler says your radius variable is type of double but your function requires array of doubles

Upvotes: 0

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