如何打乱数组的内容 [英] How to shuffle the contents of an array

问题描述

所以我的程序应该访问一个文本文档，然后做所有当前有效的爵士乐.我无法弄清楚的唯一问题是如何打乱数组的内容，而不会让它们最终彼此重叠.互联网和随机和 for 循环的多次尝试都没有结果.这是我的代码:

so my program is supposed to access a text document then do all that jazz that currently works. The only problem that I can't figure out is how to shuffle the contents of an array without having them end up on top of each other. Both internets and multiple tries with random and for loops have been unfruitful. here is my code:

import java.io.*;
import java.util.*;
public class lab_6 {
public static void main(String[] args)throws FileNotFoundException {
    Scanner input = new Scanner(System.in); //reads from keyboard
    System.out.println("What is the name of your file. ");
    String name = input.nextLine();
    Scanner reader = new Scanner(new File(name));// Open text file
    System.out.println("how many names are in your array");
    int num = input.nextInt();
    String[] names = new String[num];    
    for (int index = 0; index< names.length; index++)
    {
        names[index] = reader.nextLine();// Gets a line while there is one 
    } 
    System.out.println("\nOriginal List");
    printList(names);
    System.out.println("\nShuffled List");
    shuffle(names);
    printList(names);
    System.out.println("\nSorted List");
    Arrays.sort(names);  // this is a built in method
    printList(names);
    System.out.println("What name are you looking for");
    Scanner input1 = new Scanner(System.in); //reads from keyboard
    String find = input1.nextLine();
    int index = search(names,find);
    if(index == -1)
        System.out.println("The name was not there");
    else
        System.out.println(find+" was found at position "+index);
    System.out.println("The average length of all the names is "+averageLength(names));
}
public static void printList(String[] array) // print the list of names numbered
{
    for (int i=0; i<array.length; i++)
    {
        System.out.println((i+1)+") "+ array[i]);
    }

}
public static void shuffle (String[] array) // mix-up the array
{


}
public static int search(String[] array, String find) 
{   
    for(int i=0; i<array.length; i++) {

        if (array[i].equals(find) ) return i;

    } 
    return -1;
}
public static double averageLength(String[] array) //return the average length of the names 
{       
    int sum=0;
    for (int i=0; i<array.length; i++)
    {
        int l= array[i].length();
        sum +=l;
    }
    int average = sum/(array.length);
    return average; 

}

}

推荐答案

String[] names = ...;
Collections.shuffle(Arrays.asList(names));
// done

请注意，Arrays.asList() 返回一个可修改(但固定长度)的列表，由数组支持，而不是数组的副本.所以数组会被打乱.

Note that Arrays.asList() returns a modifiable (but fixed-length) list, backed by the array, and not a copy of the array. So the array will be shuffled.

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