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문자열을 int 배열로 변환하려고하면 Null 포인터 예외가 발생합니다. 문자열 배열이 사용되지 않습니다.내 배열에서 Null 포인터 예외가 발생합니까?
int 배열을 문자열 배열로 바꾸는 방법 또는 문제를 해결하는 방법은 무엇입니까?
여기 내 코드입니다.
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package javaapplication3;
/**
*
* @author Ivan Beazer
*/
import java.io.*;
/**
This program demonstrates the search method in
the IntBinarySearcher class.
*/
public class BinarySearchTest
{
private static String aString;
// Convert string array to string
public static String arrayToString2(String[] words, String aString)
{
StringBuilder result = new StringBuilder();
if (words.length > 0)
{
result.append(words[0]);
for (int i=1; i<words.length; i++)
{
result.append(aString);
result.append(words[i]);
}
}
return result.toString();
}
public static void main(String [] args) throws IOException
{
int result, searchValue;
String input;
// A String array of words to search.
// This is the error. netbeans says it's not being used.
String[] words = {"Jake", "Jerry", "Bill", "Lousie", "Goku", "Ivan", "John", "sarah", "kim"};
// convert string to int array
// this is my problem
int[] numbers = new int[aString.length()];
for(int i=0; i<aString.length(); i++)
numbers[i] = Character.getNumericValue(aString.charAt(i));
// this is me trying to fix the problem
if(numbers != null)
{
//do something to num
}
// Create the console input objects.
InputStreamReader reader =
new InputStreamReader(System.in);
BufferedReader keyboard =
new BufferedReader(reader);
// First we must sort the array in ascending order.
IntQuickSorter.quickSort(numbers);
do
{
// Get a value to search for.
System.out.print("Enter a value to search for: ");
input = keyboard.readLine();
searchValue = Integer.parseInt(input);
// Search for the value
result = IntBinarySearcher.search(numbers, searchValue);
// Display the results.
if (result == -1)
System.out.println(searchValue + " was not found.");
else
{
System.out.println(searchValue + " was found at " +
"element " + result);
}
// Does the user want to search again?
System.out.print("Do you want to search again? (Y or N): ");
input = keyboard.readLine();
} while (input.charAt(0) == 'y' || input.charAt(0) == 'Y');
}
}
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package javaapplication3;
/**
*
* @author Devon B
*/
/**
The IntBinarySearcher class provides a public static
method for performing a binary search on an int array.
*/
public class IntBinarySearcher
{
/**
The search method performs a binary search on an int
array. The array is searched for the number passed to
value. If the number is found, its array subscript is
returned. Otherwise, -1 is returned indicating the
value was not found in the array.
@param array The array to search.
@param value The value to search for.
*/
public static int search(int[] array, int value)
{
int first; // First array element
int last; // Last array element
int middle; // Mid point of search
int position; // Position of search value
boolean found; // Flag
// Set the inital values.
first = 0;
last = array.length - 1;
position = -1;
found = false;
// Search for the value.
while (!found && first <= last)
{
// Calculate mid point
middle = (first + last)/2;
// If value is found at midpoint...
if (array[middle] == value)
{
found = true;
position = middle;
}
// else if value is in lower half...
else if (array[middle] > value)
last = middle - 1;
// else if value is in upper half....
else
first = middle + 1;
}
// Return the position of the item, or -1
// if it was not found.
return position;
}
}
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package javaapplication3;
/**
*
* @author Devon B
*/
/**
The IntQuickSorter class provides a public static
method for performing a QuickSort on an int array.
*/
public class IntQuickSorter
{
/**
The quickSort method calls the doQuickSort method
to sort an int array.
@param array The array to sort.
*/
public static void quickSort(int array[])
{
doQuickSort(array, 0, array.length - 1);
}
/**
The doQuickSort method uses the QuickSort algorithm
to sort an int array.
@param array The array to sort.
@param start The starting subscript of the list to sort
@param end The ending subscript of the list to sort
*/
private static void doQuickSort(int array[], int start, int end)
{
int pivotPoint;
if (start < end)
{
// Get the pivot point.
pivotPoint = partition(array, start, end);
// Sort the first sub list.
doQuickSort(array, start, pivotPoint - 1);
// Sort the second sub list.
doQuickSort(array, pivotPoint + 1, end);
}
}
/**
The partiton method selects a pivot value in an array
and arranges the array into two sub lists. All the
values less than the pivot will be stored in the left
sub list and all the values greater than or equal to
the pivot will be stored in the right sub list.
@param array The array to partition.
@param start The starting subscript of the area to partition.
@param end The ending subscript of the area to partition.
@return The subscript of the pivot value.
*/
private static int partition(int array[], int start, int end)
{
int pivotValue; // To hold the pivot value
int endOfLeftList; // Last element in the left sub list.
int mid; // To hold the mid-point subscript
// Find the subscript of the middle element.
// This will be our pivot value.
mid = (start + end)/2;
// Swap the middle element with the first element.
// This moves the pivot value to the start of
// the list.
swap(array, start, mid);
// Save the pivot value for comparisons.
pivotValue = array[start];
// For now, the end of the left sub list is
// the first element.
endOfLeftList = start;
// Scan the entire list and move any values that
// are less than the pivot value to the left
// sub list.
for (int scan = start + 1; scan <= end; scan++)
{
if (array[scan] < pivotValue)
{
endOfLeftList++;
swap(array, endOfLeftList, scan);
}
}
// Move the pivot value to end of the
// left sub list.
swap(array, start, endOfLeftList);
// Return the subscript of the pivot value.
return endOfLeftList;
}
/**
The swap method swaps the contents of two elements
in an int array.
@param The array containing the two elements.
@param a The subscript of the first element.
@param b The subscript of the second element.
*/
private static void swap(int[] array, int a, int b)
{
int temp;
temp = array[a];
array[a] = array[b];
array[b] = temp;
}
}
변수 * aString *은 어디에 초기화됩니까? – Raghuram