连续3次正确回答问题后，如何将程序循环回到开头/并添加差异

Question

I'm creating a program to help with students solving y= m(x) + b. As of right now, I have the program to display the menu and evaluate if your response is correct to the answer. However, I need it to also count the number of correct answers in a row.

• If 3 correct end program and output total correct out of attempts tried.
• else if there were 3 attempts made the output a tip.

The main issue I'm having is the loop of the two (methods?). I apologize in advance if my code is atrocious, I'm having a hard time understanding methods and classes in this compared to how Python is. Anyone's suggestions or tips would be immensely helpful.

So far I've tried adding methods, and attempts at classes to certain parts of the program such as

public static void user_input(int point_of_line_cross, int slope, int y_intercept, int independent_variable) {}

and

public static test_input() {}

However, now I'm facing scoping problems as well as errors referencing certain variables.

package algebra_Tutor;
import java.util.Scanner;
class AlgebraTutor {

public static void main(String[] args){
    System.out.println("Enter 1 if you would like to solve for Y?");
    System.out.println("Enter 2 if you would like to solve for M?");
    System.out.println("Enter 3 if you would like to solve for B?");
    System.out.println("Enter 4 to Quit");


    //Asks for user input
    System.out.print("Enter your selection: ");
    }

    //Creates random # for values in formula
    int y_ = point_of_line_cross;
    int m_ = slope;
    int b_ = y_intercept; 
    int x_ = independent_variable;

public static void user_input(int point_of_line_cross, int slope, int y_intercept, int independent_variable) {

            // Creates scanner for input of menu Def as menu selector
    Scanner user_Selection = new Scanner(System.in);

            //Converts user input to an integer
    int selection = user_Selection.nextInt();
    user_Selection.close();

    y_intercept = (int) (Math.floor(Math.random() * 201) - 100);
    slope = (int) Math.floor(Math.random() * 201) - 100;
    point_of_line_cross = (int) Math.floor(Math.random() * 201) - 100;
    independent_variable = (int) Math.floor(Math.random() * 201) - 100;

            //Tests what user input was, with expected output
    if (selection  == (1)) {
        System.out.println("You chose to solve for Y: ");
        System.out.println("Y = " +slope +"("+independent_variable+")"+" + "+y_intercept);
        System.out.println("Input your answer: ");
        }
    else if (selection == (2)) {
        System.out.println("You chose to solve for M: ");
        System.out.println("M = "+"("+point_of_line_cross+" - "+y_intercept+")"+" / "+independent_variable);
        System.out.println("Input your answer: ");
        }
    else if (selection == (3)) {
        System.out.println("You chose to solve for B: ");
        System.out.println("B = "+point_of_line_cross+" - "+slope+"("+independent_variable+")");
        System.out.println("Input your answer: ");
        }
    else if (selection == (4)) {
        System.out.println("You chose to quit the program. ");
    return;
        }
        }

//Solves the problem in order to compare to User input
    int answer_y = ((m_) * (x_)) + (b_);
    int answer_m =(y_) - ((b_) / (x_));
    int answer_b =(y_) - ((m_)* (x_));
public static test_input() {
        //Problem solver defined
    Scanner answer_input = new Scanner(System.in);
    int answer = answer_input.nextInt(); 
        //Creates loop for program
    var counter = 0;
    int correct = 0;
    var answers_correct = false;
    while (!answers_correct && correct < 3) {
        if (answer == answer_y){
            counter++;
            correct++;
            System.out.println("You answered correctly");
        return;
        }
        else if (counter >= 3 && correct < 3) {
            System.out.println("Youve been missing the questions lately, let me help! ");
        }
        else
        {
            System.out.println("Try again");
            counter++;
            correct = 0;
        break;
            }
        }
    }
}

I expect the program to output correct answers out of attempts after the user completes 3 problems in a row. In addition, it needs to output a tip after 3 attempts. And then after 3 correct, it should loop back to the beginning of program.

Answer 1

It's quite late on a saturday for me to do algebra, so I will stick to suggesting changes to the structure of your program. First, you can accomplish everything with a single class to contain the questions, and score for the user. The methods in that class can be chosen via a menu in the main. I wrote a sample of how I would structure this based on standard Java OOP methodology. In my program, the main needs no static class, it loops a menu, and the choice of a question is made there. My methods hava single question, you can add as many as you like in the menu, the important thing is the structure.

 import java.util.Scanner;

//This class contains the two methods and over-all score
class Material {
private int score;
//The user chooses this or the earth method
public void sky() {

    String answer = "null"; 
    int count = 0;
    Scanner input = new Scanner(System.in);
   //within the method, is this while loop which gives a hint after 3 attempts.
    while (!answer.equals("blue") && (!answer.equals("exit"))) {
        System.out.println("What color is the sky? 'exit' to exit");
        answer = input.nextLine();
        count++;
        if (count == 3)
            System.out.println("Hint: It starts with a 'b'");
    }

    if (answer.equals("blue"))
        score += 1;//The score will increment if the choice is correct,
    else//or else leave with nothing...
        return;
}

    //This method is the same as the sky() method, just different question and answer.
public void earth() {

    String answer = "null";
    int count = 0;
    Scanner input = new Scanner(System.in);

    while (!answer.equals("iron") && (!answer.equals("exit"))) {
        System.out.println("What is the core made of? 'exit' to exit");
        answer = input.nextLine();
        count++;
        if (count == 3)
            System.out.println("Hint: It starts with a 'i'");
    }

    if (answer.equals("iron"))
        score += 1;
    else
        return;

}

public int getScore() {
    return score;
}

}

public class Questions {

public static void main(String[] args) {
    //No static methods needed, here is an instance of our test materia class.
    Material material = new Material();

    //The choice and scanner are instantiated here.
    int choice = 0;
    Scanner input = new Scanner(System.in);

    //This while loop uses a switch statement to choose the methods for the questions
    while (choice != 3) {

        if (material.getScore() == 3) {
            System.out.println("Good job, you scored three right.");
            return;
        }

        System.out.println("SCORE: " + material.getScore());
        System.out.println("Anwer questions about the sky: 1");
        System.out.println("Answer quetions about the earth: 2");
        System.out.println("Exit: 3");
        choice = input.nextInt();
       //choices are 1 , 2 for questions, and 3 to leave.
        switch (choice) {
        case 1:
            material.sky();
            break;
        case 2:
            material.earth();
            break;
        case 3:
            System.out.println("Exiting...");
            break;
        default:
            System.out.println("not a valid number choice...");

        }
    }

}// main
}// class

Answer 2

well I figured I would let you figure out how to make it loop on your own but I solved your other problems and put comments where I changed things. Hope this helps

//declared variables here. global variables must be declared static when accessed in a static method (ex: user_input())
static int y_;
static int m_;
static int b_;
static int x_;

public static void main(String[] args) {
    // Creates scanner for input of menu Def as menu selector
    Scanner user_Selection = new Scanner(System.in);

    System.out.println("Enter 1 if you would like to solve for Y?");
    System.out.println("Enter 2 if you would like to solve for M?");
    System.out.println("Enter 3 if you would like to solve for B?");
    System.out.println("Enter 4 to Quit");

    //Converts user input to an integer
    int selection = user_Selection.nextInt();

    //call user_input()
    user_input(selection);


}

public static void user_input(int selection) {

    Scanner user_Selection = new Scanner(System.in);
    int userAnswer;
    int y_intercept = (int) (Math.floor(Math.random() * 201) - 100);
    int slope = (int) Math.floor(Math.random() * 201) - 100;
    int point_of_line_cross = (int) Math.floor(Math.random() * 201) - 100;
    int independent_variable = (int) Math.floor(Math.random() * 201) - 100;

    y_ = point_of_line_cross;
    m_ = slope;
    b_ = y_intercept;
    x_ = independent_variable;


    //Tests what user input was, with expected output
    if (selection == (1)) {
        System.out.println("You chose to solve for Y: ");
        System.out.println("Y = " + slope + "(" + independent_variable + ")" + " + " + y_intercept);
        System.out.println("Input your answer: ");
        userAnswer = user_Selection.nextInt();
        /*After user enters answer we test the answer by calling test_input
         * */
       test_input(userAnswer);
    } else if (selection == (2)) {
        System.out.println("You chose to solve for M: ");
        System.out.println("M = " + "(" + point_of_line_cross + " - " + y_intercept + ")" + " / " + independent_variable);
        System.out.println("Input your answer: ");
        userAnswer = user_Selection.nextInt();
        /*After user enters answer we test the answer by calling test_input
         * */
        test_input(userAnswer);
    } else if (selection == (3)) {
        System.out.println("You chose to solve for B: ");
        System.out.println("B = " + point_of_line_cross + " - " + slope + "(" + independent_variable + ")");
        System.out.println("Input your answer: ");
        userAnswer = user_Selection.nextInt();
        /*After user enters answer we test the answer by calling test_input
         * */
        test_input(userAnswer);
    } else if (selection == (4)) {
        System.out.println("You chose to quit the program. ");
    }
}

// you forgot to include return type ex: void, int, String, double, float, etc
public static void test_input(int entered_answer) {
    //Solves the problem in order to compare to User input
    int answer_y = ((m_) * (x_)) + (b_);
    int answer_m = (y_) - ((b_) / (x_));
    int answer_b = (y_) - ((m_) * (x_));

    //Problem solver defined
    int answer = entered_answer;

    //Creates loop for program
    int counter = 0;
    int correct = 0;
    boolean answers_correct = false;

    while (!answers_correct && correct < 3) {
        if (answer == answer_y) {
            counter++;
            correct++;
            System.out.println("You answered correctly");
            return;
        } else if (counter >= 3 && correct < 3) {
            System.out.println("You've been missing the questions lately, let me help! ");
        } else {
            System.out.println("Try again");
            counter++;
            correct = 0;
            break;
        }
    }

}

`

public static void user_input(int point_of_line_cross, int slope, int y_intercept, int independent_variable)

If you give a method parameters, then when the method is called you will have to enter the values into the parameter yourself. I don't think this is what you intended because you defined what you wanted those parameter values to be here:

y_intercept = (int) (Math.floor(Math.random() * 201) - 100);
slope = (int) Math.floor(Math.random() * 201) - 100;
point_of_line_cross = (int) Math.floor(Math.random() * 201) - 100;
independent_variable = (int) Math.floor(Math.random() * 201) - 100;

In your test_input() method you wrote:

Scanner answer_input = new Scanner(System.in);
int answer = answer_input.nextInt();

.nextInt() will make the program halt and wait for user input so you don't want to use it until you are ready to get the input.

I don't really know much about the var keyword in java but rather than using var I figured you should just declare the variable type so from this:

var counter = 0;

to this:

int counter = 0;

and to get a better understanding on how methods work I recommend these two videos: Intro to java methods Java method parameters and return types

For an in depth explanation of the fundamentals of java in general then I recommend this whole playlist Java Beginner Programming

Answer 3

Side note: instead of asking the user for 1, 2, 3 or 4, you should directly ask them to enter the variable they want to solve:

Solve the equation y = m * x + b for which variable (y, m, b, quit)?

This makes the users of the program think more in the problem domain instead of some technically useless indirection.

---

As you have a Python background you should know that the indentation of the lines is important and has meaning. It's the same for Java programs. The only difference is that the Java compiler ignores the indentation completely. But Java programs are also read by humans, and for them the indentation is viable for understanding the structure of the program. The code you posted has inconsistent indentation, and you should let your IDE fix that.

---

Your program should be structured like this:

public class AlgebraTutor {

    private final Scanner in = new Scanner(System.in);
    private final PrintStream out = System.out;

    private int attempts = 0;

    void solveForY() {
        ...
    }

    void solveForM() {
        ...
    }

    void solveForB() {
        ...
    }

    void mainMenu() {
        while (true) {
            out.println("Solve the equation y = m * x + b for which variable (y, m, b), or quit?");
            if (!in.hasNextLine()) {
                return;
            }

            switch (in.nextLine()) {
            case "y":
                solveForY();
                break;

            case "m":
                solveForX();
                break;

            case "b":
                solveForB();
                break;

            case "q":
            case "quit":
                return;
            }
        }
    }

    public static void main(String[] args) {
        new AlgebraTutor().mainLoop();
    }
}