如何洗牌ArrayList [英] How to shuffle an ArrayList

问题描述

我需要一些帮助来编写一个方法，将shuffle ArrayList。我不知道什么放在我的方法。这是我到目前为止。我试图使用随机方法来随机化列表中的整数，但没有工作。

这里是我试过的代码：

  import java.util.ArrayList; 
 import java.util.Scanner; 
 
 public class Lab 11 {
 public static void main（String [] args）{
 ArrayList< Double> list = new ArrayList< Double>（）; 
 
扫描仪输入= new Scanner（System.in）; 
 System.out.print（输入整数（输入结束为0）：）; 
 double value; 
 
 do {
 value = input.nextDouble（）; //从输入中读取一个值
 
 if（value！= 0）
 list.add（value）; //添加值，如果它不在列表
} while（value！= 0）; 
 System.out.println（最大数目是+ max（list））; 
 
 System.out.print（输入五个双精度值：）; 
 for（int i = 0; i <5; i ++）
 list.add（input.nextDouble（））; 
 
 System.out.println（sum is+ sum（list））; 
 
} 
 
 public static Double max（ArrayList< Double> list）{
 if（list == null || list.size（）== 0） 
 return null; 
 
 double result = list.get（0）; 
 for（int i = 1; i  if（result< list.get（i））
 result = list.get（i） ; 
 
返回结果; 
} 
 
 public static double sum（ArrayList< Double> list）{
 double sum = 0; 
 for（int i = 0; i  sum + = list.get（i）; 
 return sum; 
} 
} 
  

解决方案

p> Collections.shuffle（arrayList）;


I need some help in writing a method that will shuffle the ArrayList. I can't figure out what to place in my method. Here is what I have so far. I tried using the random method to randomize the integers in the list but that didn't work. Can someone show me how to do this?

Here is the code I've tried:

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

public class Lab 11 {
  public static void main(String[] args) {
    ArrayList<Double> list = new ArrayList<Double>();

    Scanner input = new Scanner(System.in);   
    System.out.print("Enter integers (input ends with 0): ");
     double value;

    do {
      value = input.nextDouble(); // Read a value from the input

      if (value != 0) 
        list.add(value); // Add the value if it is not in the list
    } while (value != 0);
     System.out.println("The maximum number is " + max(list));

     System.out.print("Enter five double values: ");
     for (int i = 0; i < 5; i++)
      list.add(input.nextDouble());

    System.out.println("The sum is " + sum(list));

  }

  public static Double max(ArrayList<Double> list) {
    if (list == null || list.size() == 0)
      return null;

    double result = list.get(0);
    for (int i = 1; i < list.size(); i++)
      if (result < list.get(i))
        result = list.get(i);

    return result;
  }

  public static double sum(ArrayList<Double> list) {
    double sum = 0;
    for (int i = 0; i < list.size(); i++)
      sum += list.get(i);
    return sum;
  }
}

解决方案

Collections.shuffle(arrayList);

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