英文:
java cannot find symbol: method toLowerCase(String)
问题
我正在尝试编写一个名为isVowel的方法，该方法将返回一个布尔值，指示一个字符串是否为元音字母（即包含字符a、e、i、o、u中的任意一个，不区分大小写）。与此同时，发现在字符和字符串之间存在冲突。现在应该怎么办？谢谢大家。
public static boolean isVowel(String c)
{
char ch = Character.toLowerCase(c.charAt(0));
return ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u';
}
变量c在方法isVowel(String)中已经被定义过了。
未找到合适的方法可以将String转换为小写。
英文:
I was trying to write a method named isVowel that returns whether a String is a vowel (a single-letter string containing a, e, i, o, or u, case-insensitively). Meanwhile, find there's a confliction in character and string. Now, what to do? Thank you all.
public static boolean isVowel(String c)
{
String c = Character.toLowerCase(c);
return c=="a"||c=="e"||c=="i"||c=="o"||c=="u";
}
variable c is already defined in method isVowel(String)
!!no suitable method found for toLowerCase(String)
答案1
得分: 2
你正在传递String，但需要Character。
如果你只传递了单个字符在String中，使用以下代码将其转换为小写。
public static boolean isVowel(String s)
{
char c = Character.toLowerCase(s.charAt(0));
return c=='a'||c=='e'||c=='i'||c=='o'||c=='u';
}
英文:
You are passing String where Character is expected.
If you are passing only single character in String then use below to convert to lowercase.
public static boolean isVowel(String s)
{
char c = Character.toLowerCase(s.charAt(0));
return c=='a'||c=='e'||c=='i'||c=='o'||c=='u';
}
答案2
得分: 1
- 在同一个方法作用域中两次声明标识符
c，一次作为参数，一次作为局部变量，这将无法编译； - 将参数的类型使用
char，而不是String，否则您可能会接受长度超过1个字符的字符串；此外，String对象更加庞大； - 通常几乎不要使用
==操作符来比较字符串。而应该使用.equals(Object object)方法。
更好、更清晰、更快的方法设计如下：
public static boolean isVowel(char c) {
return "aeiouAEIOU".contains(String.valueOf(c));
}
甚至可以更好地优化：
public static boolean isVowel(char c) {
return "aeiouAEIOU".indexOf(c) != -1;
}
indexOf(int char) 返回 -1，如果未找到字符。
英文:
- You declare an identifier
ctwice in the same method scope, as a parameter, and as a local variable, which will not compile; - Use
charas a type of your parameter, instead ofString, otherwise you risk to accept the string that is longer than 1 character; besides,Stringobject is much heavier; - Generally, [almost] never compare strings with
==operator. Use.equals(Object object), instead.
Better, cleaner and faster method design would be this:
public static boolean isVowel(char c) {
return "aeiouAEIOU".contains(String.valueOf(c));
}
or even better:
public static boolean isVowel(char c) {
return "aeiouAEIOU".indexOf(c)!=-1;
}
indexOf(int char) returns -1, if char is not found.
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