如何在java中对arraylist进行排序

Question

基本上可以通过以下方式进行排序：

collections.sort（列表）；

public class GetTraders {
    private String getTraderLegalName;
    private String businessName;
    private Object status;

    public GetTraders(String getTraderLegalName, String businessName, String status) {
        this.getTraderLegalName=getTraderLegalName;
        this.businessName=businessName;
        this.status=status;
    }

public Class getResult {
    List<GetTraders> traders=new ArrayList<GetTraders>();
    public void valueGivenByuser(String legal,String business,Object status)throws Exception {
        GetTraders trade=new GetTraders(legal,business,status);
        traders.add(trade); //Adding value to arrayList
    }
}

这里的问题是，一旦我添加了traders arraylist中的所有值，我需要排序并显示为输出。我尝试使用collections.sort（），但它显示编译器异常。

Answer 1

如果仔细查看Collections API，您会发现有两个选项可供选择：

1）让GetTraders类实现可比接口并调用

public static <T extends Comparable<? super T>> void sort(List<T> list)

2）为GetTraders类创建一个新的比较器，并调用

public static <T> void sort(List<T> list, Comparator<? super T> c)

traders.sort((GetTraders trade1, GetTraders trade2) -> {
    return trade1.getBusinessName().compareTo(trade2.getBusinessName());
});

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class GetTraders1 implements Comparable<GetTraders1> {

    private String getTraderLegalName;
    private String businessName;
    private Object status;

    public GetTraders1(String getTraderLegalName, String businessName, String status) {
        this.getTraderLegalName=getTraderLegalName;
        this.businessName=businessName;
        this.status=status;
    }

    @Override
    public int compareTo(GetTraders1 that) {
        return this.getTraderLegalName.compareTo(that.getTraderLegalName);
    }

    @Override
    public String toString() {
        return "GetTraders [getTraderLegalName=" + getTraderLegalName + ", businessName=" + businessName + ", status=" + status + "]";
    }

    public static void main(String[] args) {

        GetTraders1 getTraders1 = new GetTraders1("1", "bn", "status");
        GetTraders1 getTraders2 = new GetTraders1("2", "bn", "status");
        GetTraders1 getTraders3 = new GetTraders1("3", "bn", "status");

        List<GetTraders1> list = new ArrayList<>();
        list.add(getTraders3);
        list.add(getTraders2);
        list.add(getTraders1);

        System.out.println(list);

        Collections.sort(list);

        System.out.println(list);

    }

}

2）基于比较器的解决方案

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class GetTraders2 {

    private String getTraderLegalName;
    private String businessName;
    private Object status;

    public GetTraders2(String getTraderLegalName, String businessName, String status) {
        this.getTraderLegalName=getTraderLegalName;
        this.businessName=businessName;
        this.status=status;
    }

    @Override
    public String toString() {
        return "GetTraders [getTraderLegalName=" + getTraderLegalName + ", businessName=" + businessName + ", status=" + status + "]";
    }

    public static void main(String[] args) {

        GetTraders2 getTraders1 = new GetTraders2("1", "bn", "status");
        GetTraders2 getTraders2 = new GetTraders2("2", "bn", "status");
        GetTraders2 getTraders3 = new GetTraders2("3", "bn", "status");

        List<GetTraders2> list = new ArrayList<>();
        list.add(getTraders3);
        list.add(getTraders2);
        list.add(getTraders1);

        System.out.println(list);

        Collections.sort(list, new Comparator<GetTraders2>() {

            @Override
            public int compare(GetTraders2 o1, GetTraders2 o2) {
                return o1.getTraderLegalName.compareTo(o2.getTraderLegalName);
            }

        });

        System.out.println(list);

    }

}