[英]2d array out of bound exception in for-loop
我正在使用關鍵字列密碼,並且不斷使數組超出綁定異常,我嘗試調試代碼並嘗試捕獲以了解問題,但我做不到!
public Decryption (String cipherText, String keyWord) {
cipherText = cipherText.replaceAll("\\s+","");
cipherText = cipherText.toUpperCase();
cipherText = cipherText.trim();
keyWord = keyWord.toUpperCase();
int column = keyWord.length();
int row = (cipherText.length() / keyWord.length());
if (cipherText.length() % keyWord.length() != 0)
row += 1;
char [][] matrix = new char [row][column];
int re = cipherText.length() % keyWord.length();
for (int i = 0; i < keyWord.length() - re; i++)
matrix[row - 1][keyWord.length() - 1 - i] = '*';
char[] sorted_key = keyWord.toCharArray();
Arrays.sort(sorted_key);
int p = 0, count = 0;
char[] cipher_array = cipherText.toCharArray();
Map<Character,Integer> indices = new HashMap<>();
for(int i = 0; i < column; i++){
int last = indices.computeIfAbsent(sorted_key[i], c->-1);
p = keyWord.indexOf(sorted_key[i], last+1);
indices.put(sorted_key[i], p);
for(int j = 0; j < row; j++){
if (matrix[j][p] != '*')
matrix[j][p] = cipher_array[count];
count++;
}}
}
我在以下地方遇到異常:
matrix[j][p] = cipher_array[count];
循環存在問題,如果我以j = 1開頭,它不會給我異常,但不會得到正確的結果(它不會顯示最后一行)
我要解密的密文:
YARUEDCAUOADGRYHOBBNDERPUSTKNTTTGLORWUNGEFUOLNDRDEYGOOAOJRUCKESPY
關鍵詞:
你自己
我從1開始循環時得到的結果:
判斷自己關於了解密碼的背景知識
我應該得到的是:
判斷自己的背景知識,以了解密碼學
我不確定,因為您的代碼不允許我對此進行驗證(沒有簡單的方法就無需深入研究即可檢查算法的輸出),所以...我認為解決方案是:
for (int j = 0; j < row; j++) {
if (matrix[j][p] != '*'){
matrix[j][p] = cipher_array[count];
count++;
}
}
代替:
for (int j = 0; j < row; j++) {
if (matrix[j][p] != '*')
matrix[j][p] = cipher_array[count];
count++;
}
我認為,在這種情況下,將'*'附加到字符串的策略不是解決之道-就像您所做的那樣。 在構建網格時最好追加一些字符。
按照這種方法,這里是代碼的固定版本(請檢查代碼中的注釋以了解已更改的部分):
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class Decryption {
private final String result;
public Decryption(String cipherText, String keyWord) {
cipherText = cipherText.replaceAll("\\s+", "");
cipherText = cipherText.toUpperCase();
cipherText = cipherText.trim();
keyWord = keyWord.toUpperCase();
int column = keyWord.length();
int row = (cipherText.length() / keyWord.length());
if (cipherText.length() % keyWord.length() != 0)
row += 1;
int[][] matrix = new int[row][column];
// Changed to calculate the irregular columns
int re = column - (row * column - cipherText.length());
char[] sorted_key = keyWord.toCharArray();
Arrays.sort(sorted_key);
int p, count = 0;
char[] cipher_array = cipherText.toCharArray();
Map<Character, Integer> indices = new HashMap<>();
for (int i = 0; i < column; i++) {
int last = indices.computeIfAbsent(sorted_key[i], c -> -1);
p = keyWord.indexOf(sorted_key[i], last + 1);
indices.put(sorted_key[i], p);
// Changed: Detects the need of an extra character and fills it in case of need
boolean needsExtraChar = p > re - 1;
for (int j = 0; j < row - (needsExtraChar ? 1 : 0); j++) {
matrix[j][p] = cipher_array[count];
count++;
}
if(needsExtraChar) {
matrix[row - 1][p] = '-';
}
}
result = buildString(matrix);
}
public static void main(String[] args) {
System.out.println(new Decryption("EVLNE ACDTK ESEAQ ROFOJ DEECU WIREE", "ZEBRAS").result);
System.out.println(new Decryption("EVLNA CDTES EAROF ODEEC WIREE", "ZEBRAS").result);
System.out.println(new Decryption("YARUEDCAUOADGRYHOBBNDERPUSTKNTTTGLORWUNGEFUOLNDRDEYGOOAOJRUCKESPY", "YOURSELF").result);
}
private String buildString(int[][] grid) {
return Arrays.stream(grid).collect(StringBuilder::new, (stringBuilder, ints) -> Arrays.stream(ints).forEach(t -> {
stringBuilder.append((char) t);
}), (stringBuilder, ints) -> {
}).toString().replace("-", "");
}
}
如果運行此命令,則將打印:
WEAREDISCOVEREDFLEEATONCEQKJEU
WEAREDISCOVEREDFLEEATONCE
JUDGEYOURSELFABOUTYOURBACKGROUNDKNOWLEDGETOUNDERSTANDCRYPTOGRAPHY
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