遇到陣列問題

Question

我仍然遇到了界限錯誤，我不知道爲什麼。我添加了一個print語句來查看firstList和secondList實際上是什麼，它全部搞砸了，我會在後面發佈輸出，所以也許有人可以看到發生了什麼問題。

輸出：

Names before sorting: [Justin, Butch, Mandy, Sarah, Jack, Natalie, Brent, Ashley] 
[Justin, null, null, null] 
[Justin, Butch, null, null] 
[Justin, Butch, Mandy, null] 
[Justin, Butch, Mandy, Sarah] 
[Natalie, null, null, null] 
[Natalie, Natalie, null, null] 
[Natalie, Natalie, Natalie, null] 
[Natalie, Natalie, Natalie, Natalie] 
[Justin, null] 
[Justin, Butch] 
[Sarah, null] 
[Sarah, Sarah] 
[Justin] 
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2 
    at MergeSorter.sort(MergeSorter.java:22) 
    at MergeSorter.sort(MergeSorter.java:25) 
    at MergeSorter.sort(MergeSorter.java:25) 
    at MergeSorter.main(MergeSorter.java:68) 

正如你所看到的，陣列全亂了，我不知道是什麼原因，請大家幫忙！

import java.util.*; 

public class MergeSorter 
{ 
    public static void sort(String[] names) 
    { 
     if (names.length <= 1) 
     { 
     return; 
     } 
     String[] firstList = new String[names.length/2]; 
     String[] secondList = new String[names.length - firstList.length]; 

     for (int i = 0; i < firstList.length; i++) 
     { 
     firstList[i] = names[i]; 
     System.out.println(Arrays.toString(firstList)); 

     } 
     for (int i = 0; i < secondList.length; i++) 
     { 
     secondList[i] = names[firstList.length + 1]; 
     System.out.println(Arrays.toString(secondList)); 
     } 
     sort(firstList); 
     sort(secondList); 
     merge(firstList, secondList, names); 
    } 

    private static void merge(String[] firstList, String[] secondList, String[] names) 
    { 
     int first = 0; 
     int second = 0; 
     int names1 = 0; 

     while (first < firstList.length && second < secondList.length) 
     { 
     if (firstList[first].compareTo(secondList[second]) < 0) 
     { 
      names[names1] = firstList[first]; 
      first++; 
     } 
     else 
     { 
      names[names1] = secondList[second]; 
      second++; 
     } 
     names1++; 
     } 
     while(first < firstList.length) 
     { 
     names[names1] = firstList[first]; 
     first++; 
     names1++; 
     } 
     while(second < secondList.length) 
     { 
     names[names1] = secondList[second]; 
     second++; 
     names1++; 
     } 
    } 
    public static void main(String[] args) 
    { 

     String[] names = {"Justin", "Butch", "Mandy", "Sarah", "Jack", "Natalie", "Brent", "Ashley"}; 
     System.out.println("Names before sorting: " + Arrays.toString(names)); 
     sort(names); 
     System.out.println("Names after sorting: " + Arrays.toString(names)); 
    } 
}   

Answer 1

You can use this code as well to compare the string as it is simple to compare string : 

Collections.sort(list, new Comparator<String>() { 
     @Override 
     public int compare(String s1, String s2) { 
      return s1.compareToIgnoreCase(s2); 
     } 
    }); 

Answer 2

你的錯誤是在第26行：

secondList[i] = names[firstList.length + 1]; 

這顯然會去數組的範圍之外，將其更改爲：

secondList[i] = names[firstList.length + i]; 

---

，看看你是否得到您想要的結果：

Names before sorting: [Justin, Butch, Mandy, Sarah, Jack, Natalie, Brent, Ashley] 
[Justin, null, null, null] 
[Justin, Butch, null, null] 
[Justin, Butch, Mandy, null] 
[Justin, Butch, Mandy, Sarah] 
[Jack, null, null, null] 
[Jack, Natalie, null, null] 
[Jack, Natalie, Brent, null] 
[Jack, Natalie, Brent, Ashley] 
[Justin, null] 
[Justin, Butch] 
[Mandy, null] 
[Mandy, Sarah] 
[Justin] 
[Butch] 
[Mandy] 
[Sarah] 
[Jack, null] 
[Jack, Natalie] 
[Brent, null] 
[Brent, Ashley] 
[Jack] 
[Natalie] 
[Brent] 
[Ashley] 
Names after sorting: [Ashley, Brent, Butch, Jack, Justin, Mandy, Natalie, Sarah]