java - 关于数组概念

Question

我正在寻求建议，因为在运行以下代码时出现错误:

public class Test9 {


    public static void main(String[] args) {        

        Object [] myObjects = {
                 new Integer(12),
                 new String("foo"),
                 new Integer(5),
                 new Boolean(true)
                 };
                 Arrays.sort(myObjects);
                 for(int i=0; i<myObjects.length; i++) {
                 System.out.print(myObjects[i].toString());
                 //System.out.print(" ");
                 }

    }

}

我得到的错误是:

   Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at java.lang.Integer.compareTo(Unknown Source)
    at java.util.Arrays.mergeSort(Unknown Source)
    at java.util.Arrays.sort(Unknown Source)
    at Practicequestions.Test9.main(Test9.java:18)

Answer 1

 Object [] myObjects = {
                 new Integer(12),
                 new String("foo"),
                 new Integer(5),
                 new Boolean(true)
                 };

这是一个泛型类型数组。因此，当您尝试使用 public static void sort(Object[] a) 对其进行排序时它填充运行时 ClassCastException 原因数组包含不可相互比较的元素。

Array.sort() 指定数组对象按升序排列，按照其元素的自然顺序排列。
还有另一种方法可以使用它 sort(Object[] a,Comparator c) .用你自己的逻辑实现 Comparator 并传递它。

Object[] myObjects = { new Integer(12), new String("foo"),
                new Integer(5), new Boolean(true) };
        Comparator<Object> comparator=new Comparator<Object>() {
            @Override
            public int compare(Object obj1, Object obj2) {
                if(obj1 instanceof String && obj2 instanceof String){
                    return String.valueOf(obj1).compareTo(String.valueOf(obj2));
                }else if(obj1 instanceof Integer && obj2 instanceof Integer){
                    return ((Integer) obj1).compareTo((Integer) obj2);
                }else if(obj1 instanceof Boolean && obj2 instanceof Boolean){
                    return ((Boolean) obj1).compareTo((Boolean) obj2);
                }else if(obj1 instanceof String && obj2 instanceof Integer){
                    return 1;
                }else if(obj1 instanceof Integer && obj2 instanceof String){
                    return -1;
                }else if(obj1 instanceof Boolean){
                    return -1;
                }else if( obj2 instanceof Boolean){
                    return 1;
                }
                return 0;
            }
        }; 
        Arrays.sort(myObjects,comparator);
        for (int i = 0; i < myObjects.length; i++) {
            System.out.print(myObjects[i].toString());
        }