java 生成随机数并用Java将它们排序

Generating random numbers and sorting them out in Java

提问by AppSensei

My goal is to generate random number from 0 to 100 and add them into a linkedlist object and then sort the elements.

我的目标是生成从 0 到 100 的随机数并将它们添加到链表对象中，然后对元素进行排序。

This is my code so far. I'm running into problems when I want to display the sorted elements.

到目前为止，这是我的代码。当我想显示排序的元素时遇到了问题。

The error I get: Exception in thread "main" java.util.IllegalFormatConversionException: d != java.util.Arrays$ArrayList

我得到的错误：线程“main”中的异常 java.util.IllegalFormatConversionException: d != java.util.Arrays$ArrayList

Can someone throw some light into this problem? Thank You

有人可以解决这个问题吗？谢谢

package com.LinkedLists;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.LinkedList;
import java.util.Random;
import java.util.Set;

public class InsertRandomElements {

    public static void main(String[] args) {

        // Create a random number object from 0 to 100.
        // Create an array object.
        Random r = new Random();
        int[] random = new int[100];

        // Insert random numbers into the array
        for (int i = 0; i < random.length; i++) {
            random[i] = r.nextInt(100) + 1;
        }

        // Printing out the unsorted array
        for (int i = 0; i < random.length; i++) {
            System.out.println(random[i]);
        }

        List<int[]> randomList = Arrays.asList(random);

        // Call the method in here.
        sortElements(randomList);

    }

    // Sort the elements
    private static void sortElements(Collection<int[]> values) {

        Set<int[]> set = new HashSet<int[]>(values);

        for (int[] is : set) {
            System.out.printf("Sorted Elements: %d ", values);
        }

        System.out.println();
    }

    // Calculate Sum of the elements

    // Calculate floating point average of the elements.

}

回答by Marko Topolnik

You need a List<Integer>and not a List<int[]>. Converting from a primitive array into a list of Integers is not a one-call operation, you'll actuall have to iterate over the primitive array and add to the list one by one. I don't recommend this, especially since there is no reason to use the array in the first place. For reference, you need this:

你需要一个List<Integer>而不是一个List<int[]>. 从原始数组转换为整数列表不是一次调用操作，您实际上必须遍历原始数组并逐个添加到列表中。我不推荐这样做，特别是因为没有理由首先使用数组。作为参考，你需要这个：

final List<Integer> randomList = new LinkedList<>();
for (int i : random) randomList.add(i);

When you change that, this will work:

当你改变它时，这将起作用：

System.out.printf("Sorted Elements: %s ", values);

However, it would be much simpler to sort the array itself using Arrays.sort(myArray)and then print using

但是，使用对数组本身进行排序Arrays.sort(myArray)然后使用打印会简单得多

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

On the other hand, if you used a List<Integer>right from the start, it would look like this:

另一方面，如果你List<Integer>从一开始就使用了权限，它看起来像这样：

final Random rnd = new Random();
final List<Integer> values = new ArrayList<>();
for (int i = 0; i < 100; i++) values.add(rnd.nextInt());
Collections.sort(values);
System.out.println("Sorted Elements: " + values);

回答by Yogendra Singh

Its getting confused because **int[]is an object but intis not so it assumes int[]as one element of the List, and hence returning List<int[]>not List<Integer>or List<int>(this is not possible and is causing the issue).

它变得混乱，因为 **int[]是一个对象，但int不是这样，它假定int[]为 的一个元素List，因此返回List<int[]>notList<Integer>或List<int>(this is not possible and is causing the issue)。

Please change your random to Integer[]as below, it should work fine.

请将您的随机更改Integer[]为如下所示，它应该可以正常工作。

    Integer [] random = new Integer[100];
    List<Integer> randomList = Arrays.asList(random);

To sort the list: Use Collections#sort

对列表进行排序：使用 Collections#sort

    Collections.sort(randomList);

Please remember, the method signature is: public static <T> List<T> asList(T... a)which determines the type of List to be returned based on the argument type being passed.

请记住，方法签名是：public static <T> List<T> asList(T... a)它根据传递的参数类型确定要返回的 List 类型。

Please Note:Even when you define randomas new Integer[100];, still you can leave this kind statements as is: random[i] = r.nextInt(100) + 1;. This works fine as intis promoted to Integerin those cases.

请注意：即使您定义random为new Integer[100];，您仍然可以保留这种声明：random[i] = r.nextInt(100) + 1;。如能正常工作int被提升到Integer在这些情况下。

回答by irrelephant

In this case, I think it would be easier to pass the randomarray directly to a sortElements(int[] values)method and thenconvert the array to a list.

在这种情况下，我认为将random数组直接传递给sortElements(int[] values)方法然后将数组转换为列表会更容易。

In other words, you would call sortElements(random);and then List<Integer> randomList = new LinkedList(Arrays.asList(random));to get a linked list.

换句话说，你会调用sortElements(random);然后List<Integer> randomList = new LinkedList(Arrays.asList(random));获取一个链表。

回答by Bruno

Using your code try:

使用您的代码尝试：

for (int[] is : set) {
   System.out.printf("Sorted Elements: %d ", is[0]);
}

but you still need to sort it, as mentioned in previous post

但您仍然需要对其进行排序，如上一篇文章所述