英文:
Lowercase first letter and use "_" instead of " " in Java
问题
我有一个Java程序，我想将字符串中单词的每个字符都转换为小写，并将空格“ ”替换为“_”。以下是一些示例：
- "Tall Building" --> "tall_building"
- "Red Shoes" --> "red_shoes"
- "Water" --> "water"
如果可能的话，我不想使用任何库。你介意告诉我如何做吗？我会很感激每一条建议。
英文:
I have a Java programm and I would like to make every character of a word in a String a lowercase character and replace an empty space " " by a "_". So here are some expample:
- "Tall Building" --> "tall_building"
- "Red Shoes" --> "red_shoes"
- "Water" --> "water"
I do not want to use any libarary if that is possible. Would you mind telling me how I can do that? I'd appreciate every comment.
答案1
得分: 1
public static String modifyString(String str) {
if (str == null)
return null;
if (str.isEmpty())
return str;
StringBuilder buf = new StringBuilder(str.length());
for(int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
buf.append(ch == ' ' ? '_' : Character.toLowerCase(ch));
}
return buf.toString();
}
P.S. 当然还有其他解决方案，比如 str.replace(" ", "_").toLowerCase()。我的解决方案使用了 StringBuilder，这是构建 String 的正确方式，而且没有使用正则表达式。时间复杂度为 O(n)。
英文:
public static String modifyString(String str) {
if (str == null)
return null;
if (str.isEmpty())
return str;
StringBuilder buf = new StringBuilder(str.length());
for(int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
buf.append(ch == ' ' ? '_' : Character.toLowerCase(ch));
}
return buf.toString();
}
P.S. Sure it could be more another solutions e.g. like str.replace(" ", "_").toLowerCase(). My solution uses StringBuilder which is correct way buil String and does not use Regexp. Time complexity is O(n).
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