Question

public interface Human<T> extends Comparable<T>{ }

public class Men implements Human<Men>{
  public Men(String firstName) {
    this.firstName = firstName;
  }
.....
}

public class Women implements Human<Women>{
 public Women(String firstName) {
    this.firstName = firstName;
  }
.....
}

public class MainTest{

   public static void main(String[] args) {

      List<Human> engineers= new ArrayList<Human>();
        engineers.add(new Men("A")); 
            engineers.add(new Women("A"));
        engineers.add(new Men("C"));
        engineers.add(new Men("E"));
        engineers.add(new Men("Z"));
            engineers.add(new Women("J"));
        engineers.add(new Women("B"));
        engineers.add(new Men("X"));
        engineers.add(new Men("O"));
        engineers.add(new Women("G"));   

       Collections.sort(engineers);

       System.out.println(.... print the engineers array...)
}

输出

男性（A）;男性（C）;男装（E）;男性（O）;男性（X）;男子（Z）女子（A）;女性（B）;   女性（G）;女性（AJ）;

我对arraylist的排序应为initially sorted in terms of the TYPE (Men or Women) and the secondary sort is based on firstname。我怎么能最好地完成这个呢？

我尝试了Collections.sort(....)

无法获得理想的结果。

提前致谢

Answer 1

你可能意味着

public interface Human extends Comparable<Human> {}

那就是：人类与其他人类相当。既然如此，如果你想根据类型后跟名称来比较人类，那么你的界面Human需要表达这两个属性：

public interface Human extends Comparable<Human> {
    enum Type { MAN, WOMAN }
    Type getType();
    String getName();
}

然后编写适当的compareTo()实现，同时考虑类型和名称，并使用Collections.sort()进行排序。

Answer 2

您需要使用comparator和Collections.sort(List l, Comparator c)

static final Comparator<Human> MyComparator =
                                 new Comparator<Human>() 
{
    public int compare(Human e1, Human e2) 
    {
            // Your custom comparison code goes here
    }
};

Collections.sort(engineers, MyComparator);

可以通过对象排序教程找到其他信息： http://download.oracle.com/javase/tutorial/collections/interfaces/order.html

Answer 3

比较实施based on Ryan Stewart's solution。效果很好！

Collections.sort(engineers, new Comparator<Human>() {
    @Override
    public int compare(Human o1, Human o2) {
        if(o1.getType().equals(o2.getType())) {
            return o1.getFirstName().compareTo(o2.getFirstName());
        } else {
            return o1.getType().compareTo(o2.getType());
        }
    }
});

Answer 4

class HumanComparator implements Comparator<Human>{

@Override
public int compare(Human humanObj1, Human humanObj2) {
    int index;
    if(humanObj1 instanceof Men && humanObj2 instanceof Men){
        String firstName1 = humanObj1.getFirstName();
        String firstName2 = humanObj2.getFirstName();
        index = firstName1.compareTo(firstName2);
    }else if(humanObj1 instanceof Women && humanObj2 instanceof Women){
        String firstName1 = humanObj1.getFirstName();
        String firstName2 = humanObj2.getFirstName();
        index = firstName1.compareTo(firstName2);
    }else if(humanObj1 instanceof Men && humanObj2 instanceof Women){
        index =-1;
    }else if(humanObj1 instanceof Women && humanObj2 instanceof Men){
        index =+1;
    }else{
        index =0;
    }
    return index;
}

}

您可以使用以下方式对集合进行排序：

  Collections.sort(engineers ,new HumanComparator());

Answer 5

你们是推荐这个吗？

public class HumanComparator implements java.util.Comparator<HumanBeings> {

    @Override
    public int compare(HumanBeings o1, HumanBeings o2) {
        if(o1 instanceof Men && o2 instanceof Men)
            return 0;
        else if(o1 instanceof Men && o2 instanceof Women)
            return -1;
        else if (o1 instanceof Women && o2 instanceof Men)
            return 1;

        return 0;

    }
}

....并添加更多代码以进一步按名字排序......

Answer 6

我建议使用“比较器”界面编写一个实现此接口的不同类然后在compare方法中编写适当的代码，检查实例，然后检查实例的成员。

如何根据ChildType？</parenttype>对java.util.ArrayList <parenttype>进行排序

6 个答案: