允许用户使用字符串数组.他们可以向数组添加字符串,从数组中删除字符串,搜索数组中的字符串,最终他们将能够对数组进行排序.分类是搞砸我的原因.我尝试过几种不同的方法.第一种方法是将数组转换为ArrayList,并使用Collections对ArrayList进行排序,ArrayList将转换回静态类数组.它不起作用.我尝试的第二种方法是迭代数组并尝试仅排序用户添加的字符串而不是数组中的所有内容(因为数组中有一些空值).也许我应该遍历数组,然后将非null值存储到一个新的数组中,然后我可以对它进行排序？但是如果我想在排序新数组后添加更多字符串呢？这就是为什么我停止了第二个解决方案.第三次尝试是在我的数组上使用Arrays.sort()但由于某种原因它不起作用.

这是一个例外：

Exception in thread "main" java.lang.NullPointerException

at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:290)

at java.util.ComparableTimSort.sort(ComparableTimSort.java:157)

at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)

at java.util.Arrays.sort(Arrays.java:472)

at java.util.Collections.sort(Collections.java:155)

at testingSearch.sortArray(testingSearch.java:93)

at testingSearch.main(testingSearch.java:42)

这是我的代码：

import java.util.Scanner;

import java.util.Arrays;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class testingSearch {

static String[] strArray;

static {

strArray = new String[5];

}

public static void main(String[] args) {

Scanner input = new Scanner(System.in);

while(true){

System.out.println("1. Add string to the string array.");

System.out.println("2. Remove string from the string array.");

System.out.println("3. Display strings in string array.");

System.out.println("4. Search the string array for a string.");

System.out.println("5. Sort the strings in the string array.");

int userChoice = 0;

userChoice = input.nextInt();

switch(userChoice) {

case 1:

addString();

break;

case 2:

removeString();

break;

case 3:

displayStrings();

break;

case 4:

searchArray();

break;

case 5:

sortArray();

break;

}

}

}

public static void addString(){

Scanner input = new Scanner(System.in);

System.out.println("What string do you want to add?");

String userInput;

userInput = input.nextLine();

ArrayList stringList = new ArrayList (Arrays.asList(strArray));

stringList.add(userInput);

strArray = stringList.toArray(strArray);

}

public static void removeString(){

Scanner input = new Scanner(System.in);

System.out.println("What string do you want to remove?");

String userInput;

userInput = input.nextLine();

ArrayList stringList = new ArrayList (Arrays.asList(strArray));

stringList.remove(userInput);

strArray = stringList.toArray(strArray);

}

public static void displayStrings(){

for (String s: strArray){

if (!(s == null)){

System.out.println(s);

}

}

}

public static void searchArray(){

Scanner input = new Scanner(System.in);

System.out.println("What string do you want to search the array for?");

String userInput;

userInput = input.nextLine();

ArrayList stringList = new ArrayList(Arrays.asList(strArray));

if (stringList.contains(userInput)){

System.out.println("The string array contains that string!");

}

else {

System.out.println("The string array does not contain that string...");

}

}

public static void sortArray(){

/*ArrayList stringList = new ArrayList (Arrays.asList(strArray));

Collections.sort(stringList);

strArray = stringList.toArray(strArray);*/

/*for (String s: strArray) {

if (!(s == null)){

Arrays.sort(strArray);

}

}*/

List stringList = new ArrayList(Arrays.asList(strArray));

Collections.sort(stringList);

strArray = stringList.toArray(strArray);

//Arrays.sort(strArray);

}

}