如何对同时包含字符和整数的数组进行排序？

Question

Consider the following array:

{5,"k",2,"d",3,"e"}

How can I sort the array such that the characters and integers are each grouped together and sorted:

{"d","e","k",2,3,5} 

Answer 1

You can sort an array by calling one of the sort() methods on Arrays .

In your case, you'd want to call sort(T[] a, Comparator<? super T> c) .

Since your array is an Object[] , this means that you need to implement Comparator<Object> .

Here is an example implementation that will sort your sample values as you want:

public final class MixedComparator implements Comparator<Object> {
    @Override
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public int compare(Object obj1, Object obj2) {
        Class<?> class1 = obj1.getClass();
        Class<?> class2 = obj2.getClass();

        // Sort values of same type according to their natural order
        if (class1 == class2)
            return ((Comparable)obj1).compareTo(obj2);

        // Sort values of different type by class name,
        // in descending order, so `String` sorts before `Integer`
        return class2.getName().compareTo(class1.getName());
    }
}

You then use it like this:

Object[] arr = { 5, "k", 2, "d", 3, "e" };
Arrays.sort(arr, new MixedComparator());

System.out.println(Arrays.toString(arr));

Output:

[d, e, k, 2, 3, 5]