Question

在根据名称对名称和年龄作为属性的Customer Class（用户定义）的arraylist进行排序时，Collections.sort（）方法显示错误“java.util.Comparator类型未解析。它是间接引用所需的.class文件。

package comparable;
import java.util.*;

public class Tester {
    public static void main(String[] args){
        List<Customer> custtlist=new ArrayList<Customer>();
        Customer c1=new Customer("vikas",1);
        Customer c2=new Customer("mittal",2);
        custtlist.add(c1);
        custtlist.add(c2);

        System.out.println("Before Sorting");
        Iterator<Customer> iterator = custtlist.iterator();
        while(iterator.hasNext()){
            Customer customer = (Customer) iterator.next();
            System.out.println(customer.getCustname());
        }
        Collections.sort(custtlist);   


        System.out.println("After Sorting");
        iterator = custList.iterator();

        while (iterator.hasNext()) {
            Customer customer = (Customer) iterator.next();
            System.out.println(customer.getCustName());
        }
    }
}

//Customer Class
package comparable;

public class Customer implements Comparable<Customer> {
    private String custname;
    private int age;

    public Customer(String custname, int age) {
        this.custname = custname;
        this.age = age;
    }

    public Customer() {
    }

    public String getCustname() {
        return custname;
    }

    public void setCustname(String custname) {
        this.custname = custname;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int compareTo(Customer c){
        return this.custname.compareTo(c.getCustname());
    }
}

Answer 1

你的代码中有很多错别字。在我纠正它们之后，编译成功了。我冒昧地做了一些改进和造型。

import java.util.*;

public class Tester {
    public static void main(String[] args){
        List<Customer> customersList = new ArrayList<Customer>();
        Customer c1 = new Customer("vikas", 1);
        Customer c2 = new Customer("mittal", 2);
        customersList.add(c1);
        customersList.add(c2);

        System.out.println("Before Sorting");
        for(Customer customer : customersList) {
            System.out.println(customer.getName());
        }

        Collections.sort(customersList);
        System.out.println("\nAfter Sorting");

        for(Customer customer : customersList) {
            System.out.println(customer.getName());
        }
    }
}

public class Customer implements Comparable<Customer> {
    private String name;
    private int age;

    public Customer(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Customer() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int compareTo(Customer c){
        return this.name.compareTo(c.getName());
    }
}

Collections.sort（）方法不起作用

1 个答案: