在构造函数中创建具有数组特征的数据结构

Question

I want to create a special list data structure that works like an array, in that it's like a list with values x[0], x[1], ... Any advice would be much appreciated.

I know all of my code isn't perfect I just want to figure out how to fix the one problem I've outlined below. This is some of the code I have:

public class SpecialList {

int[] specialList;
int lengthList;


public SpecialList(int x[]) {
    this.lengthList = x.length;
    this.specialList = new int[lengthList];
    this.specialList = x;
    for (int i=0; i<lengthList; i++) {
        this.specialList[i] = x[i];
    }
}

public SpecialList(SpecialList w) { 
    this.specialList = w.specialList;
}

public SpecialList doSomething(SpecialList y) { 
    int len = y.lengthList;
    //The line below is an example to show the error I get
    System.out.println(y[0]);
    //Do some other stuff to the list y
    return y;
}

//I test the code with this
public static void main(String[] args) {
    SpecialList y = new SpecialList(new int[] {14, 17, 30});
    SpecialList z = x.doSomething(y);
}

However I get the error 'array required, but SpecialList found' when I try to do stuff with y[i] like with System.out.println(y[0]); line of code.

' lengthList ' works but getting the individual values of y[i] , the list doesn't. I cant work out whats wrong with my constructor for it to not work how I want it to.

Answer 1

You can't redefine what [n] means based on what object it's applied to; that's an array-specific notation. So y[0] where y is a SpecialList instance just won't work. If it could work, List (or at least ArrayList or other implementions where direct addressing is cheap) would probably have that feature.

Although you can do that in some other languages, you can't in Java. It's just not a feature Java offers. (Which is a good thing or a bad thing depending on your point of view...) Instead, you'll have to provide get and set methods or similar, just like List does.