ArrayList对象insertionsort

Question

我正在尝试对一个充满客户对象的ArrayList进行排序。

ArrayList Cust = new ArrayList();
Cust.add(new Customer("John",15,"New York",200));
Cust.add(new Customer("Moya",25,"Randfontein",200));                        
Cust.add(new Customer("Sue",44,"Jersey",100));
Cust.add(new Customer("Mpho",23,"London",250));

我有一个外来类排序，它包含一个实现Comparable接口的插入排序方法。

public static <AnyType extends Comparable<? super AnyType>> void insertionSort(ArrayList<AnyType> a) {
        for (int p = 1; p < a.size(); p++) {
            AnyType tmp = a.get(p);
            int j;

            for (j = p; j > 0 && tmp.compareTo(a.get(j - 1)) < 0; j--) {
                a.set(j, a.get(j - 1));
            }
            a.set(j, tmp);
        }

我尝试在主类中使用此方法根据Customer的年龄（第二个元素）对ArrayList进行排序。

Sorting.insertionSort(CustList);

这给了我一个错误：找不到适合insertSort的方法（java.util.ArrayList）Sorting.insertionSort（CustList）;

帮助我__（ツ）_ /¯

根据要求，以下是完整代码：

   public interface Comparator<AnyType> {
        /**
         * Return the result of comparing lhs and rhs.
         * @param lhs first object.
         * @param rhs second object.
         * @return < 0 if lhs is less than rhs,
         *           0 if lhs is equal to rhs,
         *         > 0 if lhs is greater than rhs.
         */
        int compare( AnyType lhs, AnyType rhs );
    }
///

    public final class Customer implements Comparable<Customer> {

        String name;
        int age;
        String city;
        int loyaltyPoints;

        public Customer(String n, int a, String c, int lP) {
            name=n; age=a; city=c; loyaltyPoints=lP;
        }

        public String toString() {
            return "Customer " + name + " from " + city + " is " + age + " years old, and has loyaltypoints of " + loyaltyPoints;
        }

        public int compareTo(Customer rhs) {
            return this.age - rhs.age;
        }
    }
///
    public final class Sorting {


        public static <AnyType> void insertionSort(ArrayList<AnyType> a, Comparator<? super AnyType> cmp) {

        }



        public static <AnyType extends Comparable<? super AnyType>> void insertionSort(ArrayList<AnyType> a) {
            for (int p = 1; p < a.size(); p++) {
                AnyType tmp = a.get(p);
                int j;

                for (j = p; j > 0 && tmp.compareTo(a.get(j - 1)) < 0; j--) {
                    a.set(j, a.get(j - 1));
                }
                a.set(j, tmp);
            }
        }
    }

///
public class Test{

    public static void main(String[] args) {

        // Add some customers to an arraylist
        ArrayList Cust = new ArrayList();
        Cust.add(new Customer("John",45,"Tokyo",200));
        Cust.add(new Customer("Johna",25,"London",200));                        
        Cust.add(new Customer("James",33,"New York",100));
        Cust.add(new Customer("Jack",23,"Utah",250));                           
        Cust.add(new Customer("Janet",25,"Jersey",250));    
        Cust.add(new Customer("Jared",28,"Gotham",250));

        Sorting.insertionSort(Cust);

    }
}

Answer 1

使用ArrayList<Customer> custList = new ArrayList<>();并确保＆＃39;客户＆＃39;实现＆＃39; Comparable＆＃39;。

ArrayList Cust的问题是Java不能假设列表元素的类型，除了它们是Object，而不是Comparable。

更新：

1. 您发布的代码应该编译并运行，但是Cust.add(...)应该发出警告＆＃39;未经检查的调用“添加（E）＆＃39;作为原始类型ArrayList＆＃39;
的成员
2. 要修正警告，请将ArrayList Cust = new ArrayList<>();行替换为ArrayList<Customer> Cust = new ArrayList<>();

其他一些说明：

1. 通常，您的方法应该期望接口而不是具体类，因此您最好替换方法签名public static <AnyType extends Comparable<? super AnyType>> void insertionSort(ArrayList<AnyType> a) 使用public static <AnyType extends Comparable<AnyType>> void insertionSort(List<AnyType> a) - 注意它预计＆＃39;列表＆＃39;而不是＆＃39; ArrayList＆＃39;
2. java中的变量名以小写字母开头，即＆＃39; cust＆＃39;而不是＆＃39; Cust＆＃39;。