Java中ArrayList指定自定义类类型报错：无法解析类型求助

Hey there! Let's break down what's causing that error and fix it up for you.

The Root of the Problem #

The error "Cannot resolve Name to a Type" happens because you're using getraenk as the generic type for your ArrayList—but that's the name of a String variable in your class, not the custom Drinks (or German Getraenk) class you mentioned. Java generics require a valid class/interface type name, not a variable name, so the compiler can't find a type called getraenk.

Step-by-Step Fixes #

1. Create your custom Getraenk class (since you mentioned you have a Drinks-like custom class). Remember Java class names use PascalCase (first letter uppercase):

   public class Getraenk {
       private String name;
       // Add other properties you need, like price (preis)
       
       public Getraenk(String name) {
           this.name = name;
       }
   
       // Optional: Add getter/setter methods
       public String getName() {
           return name;
       }
   }
   

2. Fix the ArrayList generic type in your KellnerGetraenkeliste class—replace the lowercase getraenk (variable name) with uppercase Getraenk (your class name):

3. Make your constructor public (right now it's private, so you can't create instances of KellnerGetraenkeliste from outside the class).

Corrected Full Code #

Here's the updated KellnerGetraenkeliste class:

import java.util.ArrayList;

public class KellnerGetraenkeliste {
    // Class attributes
    private String kunde;
    private int anzahl;
    private String getraenk; // This is your String variable, keep it lowercase

    // Public constructor to allow instantiation
    public KellnerGetraenkeliste(String kunde, int anzahl, String getraenk) {
        super();
        this.kunde = kunde;
        this.anzahl = anzahl;
        this.getraenk = getraenk;
    }

    // Fixed generic type: uses your custom Getraenk class
    ArrayList<Getraenk> getraenkeListe = new ArrayList<>();
}

Bonus: Better OOP Practice #

If you want to store actual Getraenk objects instead of just their names in your KellnerGetraenkeliste class, you can update the getraenk attribute to use the Getraenk type directly:

// Replace private String getraenk; with:
private Getraenk getraenk;

// Update the constructor to accept a Getraenk object:
public KellnerGetraenkeliste(String kunde, int anzahl, Getraenk getraenk) {
    super();
    this.kunde = kunde;
    this.anzahl = anzahl;
    this.getraenk = getraenk;
}

Just make sure the Getraenk class is in the same package as KellnerGetraenkeliste, or add an import statement if it's in a different package.

内容的提问来源于stack exchange，提问作者Peer