スタックオーバーフロー。私は、テキストメニューを使用して単一の文字列を操作するためのさまざまなことを行うプログラムを作成しようとしています。メソッドの1つは、文字列を文字列の配列に変換します。これは正常に機能します。ただし、配列として操作するすべてのメソッド（1つは出力し、1つは語順を逆にし、もう1つは交換ソートメソッドを使用してソートします）は、呼び出されるとNullPointerExceptionを返します。私はコード全体を調べましたが、コードがどこから来ているのかわかりません。これがすべてのコードを含む.Javaファイルです。私の問題は、下部にあるprintArray（）、reverse（）、およびsort（）メソッドを呼び出したときにのみ発生します。ありとあらゆる助けをいただければ幸いです。ずさんなコードで申し訳ありませんが、私はまだそれをクリーンアップしていません。
コード：
/*
Computer Programming Lab 11
Jim Kimble
3 Mar 2013
Work with strings and implementing a menu.
Acknowledgements:
Uses main structure of HUTPanel as designed at UMU, 2002-2012
*/
import java.io.*;
import java.awt.*;
import javax.swing.*;
public class HUTPanel extends JPanel
{
/***************************************************
* Class-level data members should be declared here.
***************************************************/
int numVowels;
String[] words;
String str;
String vowels;
String menuChoice;
String oString = "A tong lime ago, a daggy shog bossed a cridge over a pillmond,\n"
+"When in the course of human events\n"
+"Mary had a little lamb.\n"
+"The girls' basketball team repeated as tournament champion this weekend.";
public HUTPanel(JFrame frame)
{
// Set panel background color
setBackground(Color.WHITE);
setLayout(null);
setPreferredSize(new Dimension(810, 410));
/***************************
* Now add your code below:
***************************/
// Create a frame around this panel.
frame.setTitle("Computer Programming Lab/Program # 11");
frame.getContentPane().add(this);
str = "A tong lime ago, a daggy shog bossed a cridge over a pillmond,\n"
+"When in the course of human events\n"
+"Mary had a little lamb.\n"
+"The girls' basketball team repeated as tournament champion this weekend.";
System.out.println("Lab 11: Text Manipulation");
//getTheText();
System.out.println("The string is: '"+str+"'.");
handleTheMenu();
} // end of constructor
/*************************
* Add your methods here:
*************************/
// Get a text sequence from the keyboard and put it in str
public void getTheText()
{
Boolean inputDone = false;
while (!inputDone)
{
System.out.print("Enter your text: ");
inputDone = grabText();
}
}
private Boolean grabText()
{
try {
BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
menuChoice = inputReader.readLine();
return true;
}
catch(IOException e)
{
System.out.println("Error reading input. Please try again.");
}
return false;
}
public void handleTheMenu()
{
int choice = -1;
Boolean OK;
while (choice != 0)
{
choice = -1;
System.out.println("Menu:");
System.out.println();
System.out.println(" 1. Count the vowels"); //"There are ... vowels in the text."
System.out.println(" 2. Remove all letter e's"); //then print it.
System.out.println(" 3. Replace all t's with '+'"); //then print it
System.out.println(" 4. Search for a requested word (will reset the string)"); //Does 'word' exist in the text?
System.out.println(" 5. Print the words on individual lines");
System.out.println(" 6. Reset the string.");//Reset the string to the original
System.out.println(" 7. Put the words in an array"); //then print it
System.out.println(" 8. Reverse the text word order"); //then print it
System.out.println(" 9. Sort the words in an array"); //Once the words are put into an array
System.out.println();
System.out.print(" 0 to quit --> ");
OK = grabText();
if (OK)
{
try
{
choice = Integer.parseInt(menuChoice);
}
catch(NumberFormatException e)
{
System.out.println("Not a number; please try again.");
System.out.println();
}
switch(choice)
{
case 0: System.out.println();
System.out.println("Thank you.");
break;
case 1: countVowels();
break;
case 2: removeAllEs();
break;
case 3: changeTToPlus();
break;
case 4: find();
break;
case 5: listWords();
break;
case 6: reset();
break;
case 7: makeArray();
break;
case 8: reverse();
break;
case 9: sort();
break;
default: System.out.println("Not a valid choice; please try again.");
}
}
}
}
private void countVowels() {
//count the vowels in str
vowels = "aeiouAEIOU";
numVowels = 0;
for( int i = 0; i < vowels.length(); i ++) {
for(int j = 0; j < str.length(); j++) {
if (str.charAt(j) == vowels.charAt(i)) {
numVowels += 1;
}
}
}
System.out.println("The string has " + numVowels + " vowels in it.");
}
private void removeAllEs() {
String str3 = str.replace('e', ' ');
System.out.print(str3);
str = str3;
}
private void changeTToPlus() {
String str2 = str.replace('t', '+');
System.out.println(str2);
str = str2;
}
private void find() {
str = oString;
getTheText();
if(str.indexOf(menuChoice) != -1)
{
System.out.println("The word " +menuChoice+ " is at index " +str.indexOf(menuChoice));
}
else
{
System.out.println("The word " +menuChoice+ " is not in the string.");
}
}
private void listWords() {
int pos = 0;
int i = 0;
while(i > -1)
{
i = str.indexOf(' ', pos);
if (i > -1)
{
System.out.println(str.substring(pos, i));
pos = i + 1;
}
}
}
private void reset() {
str = oString;
System.out.println();
System.out.println("String reset.");
System.out.println();
}
private void makeArray() {
int n = 1;
String[] words = new String[n];
int pos = 0;
int i = 0;
int j = 0;
while(j > -1)
{
for (i = 0; i < 1000; i++)
{
n += 1;
j = str.indexOf(' ', pos);
if (j > -1)
{
words[i] = str.substring(pos, j);
pos = j + 1;
}
}
}
//printArray();
}
//***FIX***
private void printArray() {
for (int k = 0; k < words.length -1; k++){
System.out.println(words[k]);
}
}
//***FIX***
private void reverse() {
int i = 0;
int j = words.length - 1;
String temp;
while (i < j){
temp = words[i];
words[i] = words[j];
words[j] = temp;
i++;
j--;
}
}
private void sort() {
String temp = "";
for (int i = 1; i < words.length - 1; i++) {
for (int j = i + 1; j < words.length; j++) {
int x = words[i].compareTo(words[j]);
if (x > 0) {
temp = words[i];
words[i] = words[j];
words[j] = temp;
}
}
}
for (int p = 0; p < words.length -1; p++) {
System.out.println(words[p]);
}
}
}