[英]How to replace characters in a string in Java without using .replace?
The goal of this program is to prompt the user for a single character and a phrase, and then replace any instances of that character within that phrase with a '$'. 此程序的目标是提示用户输入单个字符和短语,然后用'$'替换该短语中该字符的任何实例。 My program below does just that, but when I showed it to my professor I was told that I cannot use .replace in the methods I built, so I have to figure out a way to not use that.
我的程序就是这样做的,但是当我向我的教授展示时,我被告知我不能在我构建的方法中使用.replace,所以我必须找到一种不使用它的方法。 I have worked at it for a while, and thus far I know that I can replace it with a for loop, but after several frustrating iterations, I can't seem to get it right.
我已经工作了一段时间,到目前为止我知道我可以用for循环替换它,但经过几次令人沮丧的迭代之后,我似乎无法做到正确。 Excuse me if my code looks funky, I am still an introductory java student so I'm still learning the basics.
对不起,如果我的代码看起来很时髦,我仍然是一名入门的java学生,所以我还在学习基础知识。 I have provided a proposed solution at the end of my code snippet below.
我在下面的代码片段末尾提供了一个建议的解决方案。
public static char getKeyCharacter(String userInput) {
char keyCharacter;
Scanner inputStream = new Scanner(System.in);
while(userInput.length() > 1)
{
System.out.println("Please enter a SINGLE character to use as key: ");
userInput = inputStream.nextLine();
}
keyCharacter = userInput.charAt(0);
return keyCharacter;
}
public static String getString(String userResponse) {
Scanner inputStream = new Scanner(System.in);
String theString;
while(userResponse.length() > 500) {
System.out.println("Please enter a phrase or sentence >= 4 and <=500 characters: ");
userResponse = inputStream.nextLine();
}
while(userResponse.length() < 4) {
System.out.println("Please enter a phrase or sentence >= 4 and <=500 characters: ");
userResponse = inputStream.nextLine();
}
theString = userResponse;
return theString;
}
public static String maskCharacter(String theString, char keyCharacter){
String maskedString = "";
final char mask = '$';
maskedString = maskedString + theString.replace(keyCharacter, mask);
System.out.println("String with " + keyCharacter + " masked: ");
return maskedString;
}
public static String removeCharacter(String theString, char keyCharacter) {
String modifiedString = " ";
final char replaceChar = ' ';
modifiedString = modifiedString + theString.replace(keyCharacter, replaceChar);
System.out.println("String with " + keyCharacter + " removed:");
return modifiedString;
}
public static int countKey(String theString, char keyCharacter) {
int charCount = 0;
for (int c = 0; c < theString.length(); c++) {
if (theString.charAt(c) == keyCharacter) {
charCount++;
}
}
System.out.println("Occurences of " + keyCharacter + " in string:");
return charCount;
}
} }
I believe the solution is will look something like this, but thus far I've been unsuccesful - 我相信解决方案看起来会像这样,但到目前为止我一直不成功 -
public static String maskCharacter(String theString, char keyCharacter){
String maskedString = "";
final char mask = '$';
for (int k = 0; k < theString.length(); k++) {
if (theString.charAt(k) == keyCharacter) {
keyCharacter = mask;
}
System.out.println("String with " + keyCharacter + " masked: ");
return maskedString;
}
My issue lies in making the maskedString = theString with all the keyCharacters replaced by mask. 我的问题在于使用mask替换所有keyCharacters,使maskedString = theString。 For the record, I have yet to learn anything about those fancy arrays, so if there is a way to do this using a simple for loop I would greatly appreciate it.
为了记录,我还没有学习任何关于那些花哨的数组,所以如果有一种方法可以使用一个简单的for循环来做到这一点我会非常感激。 Thank you for the assistance in advance!
感谢您的帮助!
I would use a StringBuilder
and String#toCharArray()
with a simple for-each
loop. 我会使用
StringBuilder
和String#toCharArray()
以及一个简单的for-each
循环。 Like, 喜欢,
public static String maskCharacter(String theString, char keyCharacter){
StringBuilder sb = new StringBuilder();
for (char ch : theString.toCharArray()) {
if (ch == keyCharacter) {
sb.append('$'); // <-- mask keyCharacter(s).
} else {
sb.append(ch); // <-- it isn't the character to mask
}
}
return sb.toString();
}
I wouldn't use a StringBuilder
: just use the result of toCharArray()
directly: 我不会使用
StringBuilder
:直接使用toCharArray()
的结果:
char[] cs = theString.toCharArray();
for (int i = 0; i < cs.length; ++i) {
if (cs[i] == keyCharacter) cs[i] = '$';
}
return new String(cs);
Not only is it more concise, but: 它不仅更简洁,而且:
public static String maskCharacter(String theString, char keyCharacter){ public static String maskCharacter(String theString,char keyCharacter){
String masked = "";
for (int i = 0 ; i < theString.length() ; i++) {
if (theString.charAt(i) == keyCharacter) {
masked += "$";
}
else {
masked+=theString.charAt(i)+"";
}
}
return masked;
} }
An answer that only uses string concatenation and basic character access. 仅使用字符串连接和基本字符访问的答案。
You seem to know that you can concatenate something to a string and get a different string. 您似乎知道可以将某些内容连接到字符串并获取不同的字符串。
maskedString = maskedString + ...;
You also know you can build a for-loop that gets each individual character using .charAt()
您还知道可以构建一个使用
.charAt()
获取每个单独字符的for循环
for (int k = 0; k < theString.length(); k++) {
char nch = theString.charAt(k);
}
You can check equality between chars 您可以检查字符之间的相等性
if (nch == keyCharacter)
... assuming you know about else-branches, isn't it clear you just need to put them together? ...假设你知道其他分支,是不是很清楚你只需要将它们放在一起?
if (nch == keyCharacter) {
// append '$' to maskedString
}
else {
// append nch to maskedString
}
Of course this creates a new string on every loop iteration so it is not terribly efficient. 当然,这会在每次循环迭代时创建一个新字符串,因此效率不高。 But I don't think that's the point of the exercise.
但我认为这不是演习的重点。
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