代码不会启动

Question

Ok, this code won't launch. It will launch the other class. Yes I did name the The class This, so no error there.

package com.thekyle.hi;

class This {
    double b;
    int e;
    double val;

    This(double base, int exp) {
        this.b = base;
        this.e = exp;

        this.val = 1;
        if (exp==0) return;
        for (; exp > 0; exp--)
            this.val = this.val * base;
System.out.println(exp);
    }

    double get_pwr() {
        return this.val;
    }
}

So any way to make this launch. Also running configurations doesn't work.

Answer 1

You don't have main method so your code will not execute. Main method is entry point to your application.so You can write main method in your class as

public static void main(String []args)
{
    This obj = new This(2,2);
    System.out.println(get_pwr());
}

Answer 2

Like others have commented, this code will not run because your main method is probably in different class . It looks like you are trying to make your This class be an object in your main method. Here are some code examples and explanations of what I changed.

This.java

1. All of the this keywords you have put in the class are redundant, so I removed them.
2. Your for loop is improperly set up. I created it with an index of i which is assigned the value of exp.

3. To make a variable equal to itself times something else, you can use *= . For example, a=a*b is equivalent to a*=b .

    class This { double b; int e; double val; This(double base, int exp) { b = base; e = exp; val = 1; if (exp == 0) { return; } for (int i = exp; i > 0; i--) { val*=base; } } double get_pwr() { return val; } }

MyClass.java

1. This class contains the main method, which is the method that the Java virtual machine looks for to start.
2. I've created an object of your This class. You made it's constructor take a double base and an int exp, so I have given it a double and an int.

3. After creating the object, the calculations are complete. You made a getter for the variable val which has the result of your computation. Simply call the method and print it out, which is the the System.out.println() call does.

    public class myClass { public static void main(String[] args) { This myThis = new This(2, 6); System.out.println(myThis.get_pwr()); } }