java 数组排序降序
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Array Sorting Descending Order
提问by Hugo Diaz
I'm a new programmer to java, been using this website a lot to learn the ways. Today I've stumbled into another problem towards a program I'm doing for practice.
我是 Java 的新程序员，经常使用这个网站来学习方法。今天，我在为练习而做的一个程序中遇到了另一个问题。
I have an array:
我有一个数组：
final int EXAMS = 5;
int[] scores = new int [EXAMS];
The values for this array are then asked from the user through a Scanner object:
然后通过 Scanner 对象向用户询问此数组的值：
for (int index = 0; index < EXAMS; index++)
{
System.out.println("Enter the score for " + (index+1) +":");
scores[index] = kb.nextInt();
if (scores[index] < 0){
System.out.println("The number you have entered is invalid.");
scores[index] = kb.nextInt();
}
}
I managed to make an ascending order sorting of the values "scores[]":
我设法对值“scores[]”进行升序排序：
Arrays.sort(scores);
System.out.println("The sorted int array is:");
for (int number : scores)
{
System.out.println("Number = "+ number);
}
But I want the sorting to be in descending order. When I put the
但我希望排序按降序排列。当我把
Arrays.sort(scores, Collections.reverseOrder());
Arrays.sort(scores, Collections.reverseOrder());
I get an error saying: "no suitable method found for sorting." Please help.
我收到一条错误消息：“找不到合适的排序方法。” 请帮忙。
采纳答案by Eran
There's no sortmethod in Arraysclass that accepts an int[]and a Comparator. The sortmethods in the Arraysclass that accept a Comparatorrequire an array of reference type (while an int[]is an array of a primitive type).
有没有sort在方法Arrays的类，它接受int[]和Comparator。所述sort的方法中Arrays类接受一个Comparator需要引用类型的阵列（而一个int[]是基本类型的阵列）。
If you change the type of your scoresarray from int[]to Integer[], your code will work, since the method public static <T> void sort(T[] a, Comparator<? super T> c)of the Arraysclass will match your Arrays.sort(scores, Collections.reverseOrder());call.
如果你改变你的类型scores的数组int[]到Integer[]，你的代码将工作，因为该方法public static <T> void sort(T[] a, Comparator<? super T> c)的的Arrays类将符合您的Arrays.sort(scores, Collections.reverseOrder());通话。
final int EXAMS = 5;
Integer[] scores = new Integer [EXAMS]; // the only required change
for (int index = 0; index < EXAMS; index++) {
System.out.println("Enter the score for " + (index+1) +":");
scores[index] = kb.nextInt();
if (scores[index] < 0){
System.out.println("The number you have entered is invalid.");
scores[index] = kb.nextInt();
}
}
Arrays.sort(scores, Collections.reverseOrder());
System.out.println("The sorted int array is:");
for (int number : scores) {
System.out.println("Number = "+ number);
}
回答by alfasin
The following works (using the IntegerObjects instead of primitive int):
以下工作（使用IntegerObjects 而不是 original int）：
Integer[] test = {1, 2, 4, 3, 5};
Arrays.sort(test, Collections.reverseOrder());
System.out.println(Arrays.toString(test)); // [5, 4, 3, 2, 1]
回答by Danny Varela
Collections.reverseOrder()
Won't work because the array is of primitive type. You can change from int to Integer or try something different like:
不会工作，因为数组是原始类型。您可以将 int 更改为 Integer 或尝试不同的方法，例如：
Arrays.sort(scores);
ArrayUtils.reverse(scores);
Your final option would be to make your own code.
您的最终选择是制作自己的代码。
回答by Nitesh Virani
You just need to change your array type from Primitive typeto Primitive wrapper classi.e. int[] scores = new int [EXAMS]to Integer[] scores = new Integer[EXAMS]
你只需要改变你的数组类型从Primitive type到Primitive wrapper classieint[] scores = new int [EXAMS]到Integer[] scores = new Integer[EXAMS]
Arrays.sortaccept wrapper array in the first argument not primitive.
Arrays.sort在第一个参数中接受不是原始参数的包装器数组。
回答by Parag Kadam
Arrays.sort(a, Collections.reverseOrder());
does not work with primitives. Try this,
不适用于原语。试试这个，
Integer[] a = new Integer[]{1,2,3,5,4};
Arrays.sort(a,Collections.reverseOrder());
for(int i:a)
{
System.out.println(i);
}
回答by pramod kumar
There is no sort method for arrays in java.But ArrayList have a sort method.You can the below code to sort the list in reverse order.
java中没有数组的排序方法。但是ArrayList有排序方法。可以通过下面的代码对列表进行逆序排序。
List l=new ArrayList();
l.add(5);
l.add(1);
l.add(2);
l.add(3);
Collections.sort(l,Collections.reverseOrder());
System.out.println(l);
