如何多次调用方法来更改变量？

Question

I am trying to call an accelerate method on a speed variable that adds 5 to the speed variable each time it is called. I'm able to do it once in the constructor:

public int getAccelerate() {
    accelerate = (speed + 5);
    return accelerate;
}

and display it using

System.out.println(car1.getAccelerate());

but that only works once, which displays 105 if the speed variable is 100.

My question is: how do I update the speed variable each time the accelerate method is called to reflect the new speed value?

Calling it 5 times gives me the output

105
105
105
105
105

where I am trying to get the output

105
110
115
120
125

by calling the same method 5 times.

Answer 1

Think about what is happening. Your method takes speed , adds 5 to it, and puts that value in the variable accelerate . Then it returns accelerate . So every time, you change accelerate based on speed , but you never change speed ! So for example, if speed is 100 , the first call will return 100 + 5 , the second call will return 100 + 5 , and so on.

If you want this to work properly, change accelerate each time:

public int getAccelerate()
{
    accelerate = (accelerate + 5);
    return accelerate;
}

Or you could change speed each time:

public int getAccelerate()
{
    speed = (speed + 5);
    return speed;
}