Eclipse says "cannot be resolved to a type" [duplicate]

Question

So I'm doing an assignment for school and its my first CS class. We have to create a Mars Landing Simulator. On the line,

MarsLander lander = new MarsLander(850, engineIgnitionTime, engineThrust);

The code on that line says "MarsLander cannot be resolved to a type". Why is it saying that? I've been stuck on this for three days. I have no clue what I'm doing.

import java.util.Scanner;


public class MarsLandingSimulator {

    private static final double ALTITUDE_START = 10000.0;
    

    public static void main(String[] args) {
        
        System.out.println("-----------------------------------------");
        System.out.println("|                                       |");
        System.out.println("| Welcome to the Mars Landing Simulator |");
        System.out.println("|                                       |");
        System.out.println("-----------------------------------------");
        System.out.println();
        System.out.println(""
                + "This program will simulate the final phase\n"
                + "of a rocket landing on Mars! \n\n"
                + "The rocket will free-fall from a height of\n"
                + "10,000 meters until the engines are ignited\n"
                + "at a certain time after the fall starts.\n\n"
                + "Your job is to choose the engine ignition\n"
                + "time and engine thrust to make a safe landing.\n\n"
                + "The lander's engines have enough fuel for\n"
                + "a 300 second burn.");
        System.out.println();
        
        Scanner keyboard = new Scanner(System.in);
        String input = "";

        // outer loop to give the user multiple chances
        do {
            
            printLine(40);
            System.out.printf("%-45s","Enter the engine ignition time (seconds): ");
            input = keyboard.nextLine();
            double engineIgnitionTime = Double.parseDouble(input);

            System.out.printf("%-45s","Enter the engine thrust (Newtons): ");
            input = keyboard.nextLine();
            double engineThrust = Double.parseDouble(input);

            // Create an instance of the MarsLander
            // During the final phase of landing, the mars lander
            // will have a mass of 850kg
            MarsLander lander = new MarsLander(850, engineIgnitionTime, engineThrust);
            
            // Set the initial altitude
            lander.setAltitude(ALTITUDE_START);
            
            // run the simulation.
            runSimulation(lander);
            
            // try again prompt
            System.out.println("\n");
            System.out.printf("Would you like to run another simulation? ");
            input = keyboard.nextLine();
        } while(input.toLowerCase().startsWith("y"));
                
        
        System.out.println("\n");
        System.out.println("Thank you for trying the Mars Landing Simulator.");
        
        keyboard.close();
    }
    
    /**
     * Helper method to print out a line with a given length.
     * @param length
     */
    private static void printLine(int length) {
        for (int i=0; i<length; i++) {
            System.out.print("-");
        }
        System.out.print("\n");
    }
    
    /**
     * Performs a simulation given a MarsLander object
     * with initial conditions pre-set.
     * @param lander
     */
    private static void runSimulation(MarsLander lander) {
        
        // Set the time increment
        double dt = 0.01;
        
        // Set the maximum simulation time in seconds
        double simulationTimeMax = 20 * 60; 
        
        // index for displaying the result
        int displayIndex = 0;
        int displayPeriod = (int)(1.0 / dt);
        
        System.out.println("\n");       
        System.out.println("LANDING TELEMETRY:");
        // print the column headers
        System.out.printf("%10s%10s%10s%10s\n", "ET(s)", "A(m)", "v(m/s)","a(m/s^2)");
        printLine(40);
        
        // Simulate the fall of the Rocket.
        for (double simulationTime = 0.0; simulationTime<simulationTimeMax && lander.getAltitude()>0; simulationTime+=dt) {
            
            // Update the lander status at each point in the simulation
            lander.update(simulationTime);
            
            // Update the report output every display period to limit the amount of data
            // displayed to the user.
            if ((displayIndex++ % displayPeriod) == 0) {
                lander.display();
            }
        }
        // display the final state of the lander
        lander.display();
        
        // Create the landing report
        printLine(40);
        System.out.println();

        // Create the final report
        System.out.println("LANDING REPORT:");
        printLine(40);
        System.out.printf("%-20s %,10.1f (s)\n", "Elapsed Time:", lander.getTime());
        System.out.printf("%-20s %,10.1f (s)\n", "Engine Burn Time:", Math.abs(lander.getEngineBurnDuration()));
        System.out.printf("%-20s %,10.3f (m/s)\n", "Terminal Velocity:", Math.abs(lander.getVelocity()));
        System.out.printf("%-20s %,10.1f (%%)\n", "Fuel Remaining:", 100.0 * (MarsLander.ENGINE_MAX_BURN_DURATION - lander.getEngineBurnDuration()) / MarsLander.ENGINE_MAX_BURN_DURATION);
        
        
        // Evaluate the landing         
        // Did we make it to the ground in time?
        String missionStatus = "";
        if (lander.getAltitude() > ALTITUDE_START) {
            missionStatus = "Landing failed.\n"
                    + "The lander has returned to orbit\n"
                    + "and is out of fuel for a second attempt.";
        }
        else if (lander.getAltitude()>1.0) {
            missionStatus = "Landing failed.\n"
                    + "Landing engine fuel has been exhausted.\n"
                    + "The lander has sustained major damage\n"
                    + "and is no longer functioning.";
        } 
        // we made it to the ground but how fast were we going?
        // A landing speed greater than 1.0 m/s is considered a crash. 
        // Major damage to the lander will have occurred
        else if (Math.abs(lander.getVelocity()) > 1.0) {
            missionStatus = "Landing failed.\n"
                    + "Terminal Velocity exceeded maximum safety limits.\n"
                    + "The lander has sustained major damage\n"
                    + "and is no longer functioning.";
        } 
        // A landing speed between 1.0 and 0.1 m/s is considered a hard landing.
        // Minor damage may have occurred.
        else if (Math.abs(lander.getVelocity()) > 0.1) {
            missionStatus = "Hard landing.\n"
                    + "Terminal Velocity exceeded optimal safety limits.\n"
                    + "The lander has sustanined minor damage\n"
                    + "but is still mostly operational.";
        } 
        // A landing speed between 0.1 and 0.01 meters per second is a good landing.
        else if (Math.abs(lander.getVelocity()) > 0.01) {
            missionStatus = "Good landing.\n"
                    + "The lander has not sustained any damage.\n"
                    + "There is a slight probability that\n"
                    + "some sensitive experiments were disturbed.";
        } 
        
        // A landing speed below 0.01 meters per second is a perfect landing
        else {
            missionStatus = "Perfect landing.\n"
                    + "No damage to the lander or experiments on board.\n"
                    + "Congratulations!";
        }
        System.out.printf("\n%s\n%s\n","Mission Status:", missionStatus);
        printLine(40);
        
    }

}

Answer 1

It seems like Eclipse cannot find the MarsLander class and thus it cannot instantiate a MarsLander variable.

You either forgot to define the MarsLander class within your project or you did not import the whole project's files if this was an example from your teacher.