java - java 中的错误 - 查找 ArrayList 中的最大值

Question

以下是我为回答该问题而编写的程序 -

“现在使用 ArrayList 和 Integer 包装类来存储值，并通过使用 Scanner 类从控制台读取输入来初始化元素。扩展程序以识别 ArrayList 中的 n 个最大值。”

import java.util.ArrayList;
import java.util.Scanner;    

public class ArraylistInput {
/**
 * @param args
 */
public static void main(String[] args) {

    ArrayList<Integer> val = new ArrayList<Integer>();
    Scanner in = new Scanner(System.in);
    System.out.println("Enter the length of you Array List ");
    int nos = in.nextInt();
    // Recorrd the input numbers
    for (int i = 0 ; i < nos; i++)
    {
        System.out.println("Enter values for the ArrayList ");
        int Input = in.nextInt();
        val.add(Input);
    }

    // Display the arraylist
    for (int j = 0; j < nos; j++)
    {
        int x = val.get(j);
        System.out.println("Index " + (j+1) + ": " +  x);
    }
    System.out.println("How meny maximmum values do you want? ");
    int max =0; // initial max value
    int nmax = in.nextInt(); // number of maximum values
    int length = val.size(); // size of the arraylist

    // finding the maximum values in ascending order without sorting
    for (int h = 1; h <= nmax ; h++)
    {           
        for (int k=0;k < length; k++)
        {
            if (val.get (k) > max)
            {
                 max = val.get(k);
            }               
        }
        System.out.println ("maximmum = " + max);
        int z = val.indexOf(max); // removing the higest value after printing
        val.remove(z);
    }           
    }
}

Output and Error:

Enter the length of you Array List

3

Enter values for the ArrayList

12

Enter values for the ArrayList

45

Enter values for the ArrayList

8

Index 1: 12 Index 2: 45 Index 3: 8

How meny maximmum values do you want?

2

maximmum = 45

Exception in thread "main" maximmum = 45 java.lang.ArrayIndexOutOfBoundsException: -1 at java.util.ArrayList.elementData(Unknown Source) at java.util.ArrayList.remove(Unknown Source) at ArraylistInput.main(ArraylistInput.java:46)

Answer 1

我会执行以下操作:

Collections.sort(myList, Collections.reverseOrder());
List<Integer> maxn = myList.subList(0, n);
System.out.printf("The maximum %d values are: %s%n", n, maxn);
maxn.clear(); //This clears the sublist and removes its elements from the source list

这将为您提供一个列表，其中包含列表中最多 n 个元素。