Java - 为什么我不能使用 charAt() 来查看一个字符是否等于另一个字符？
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Java - Why can't I use charAt() to see if a char equals another?
提问by Mayron
I want to see if a character in my string equals a certain other char value but I do not know what the char in the string is so I have used this:
我想看看我的字符串中的一个字符是否等于某个其他字符值，但我不知道字符串中的字符是什么，所以我使用了这个：
if ( fieldNames.charAt(4) == "f" )
But I get the error:
但我收到错误：
"Operator '==' cannot be applied to 'char', 'jav.lang.String'"
But "g" == "h"seems to work and I know you can use '=='with char types.
但"g" == "h"似乎有效，我知道您可以使用'=='char 类型。
Is there another way to do this correctly? Thanks!
有没有另一种方法可以正确地做到这一点？谢谢！
采纳答案by Madhawa Priyashantha
if ( fieldNames.charAt(4) == 'f' )
because "f"is a Stringand fieldNames.charAt(4)is a char. you should use 'f'for check char
因为"f"是一个String并且fieldNames.charAt(4)是一个char。你应该'f'用于检查字符
"g" == "h"works because both g and h are Strings
"g" == "h"有效，因为 g 和 h 都是 Strings
and you shouldn't use "g" == "h"you should use "g".equals("h")instead .
you can use == for primitivedata types like char,int,boolean....etc.but for the objectslike String it's really different.
To know why read this
你不应该使用 "g" == "h"你应该使用"g".equals("h")。您可以将 == 用于primitive诸如char,int,boolean....etc 之objects类的数据类型，但对于诸如 String 之类的数据类型，它确实不同。
要知道为什么读这个
but you can use also
但你也可以使用
'g' == 'h'
you should wrap Strings by double quotation and char by single quotation
你应该用双引号包裹字符串，用单引号包裹字符
String s="g";
char c='g';
but char can only have one character but String can have more than one
但 char 只能有一个字符，而 String 可以有多个
String s="gg"; valid
char c='gg'; not valid
回答by And
I was having the same problem, but I was able to solve it using:
我遇到了同样的问题，但我能够使用以下方法解决它：
if (str.substring(0,1).equals("x") )
the substring can be used in a loop str.substring(i, i + 1)
子字符串可以在循环中使用 str.substring(i, i + 1)
charAt(i).equals('x') will not work together
charAt(i).equals('x') 不能一起工作
回答by J?rgen Bauer
This works:
这有效：
if (String(fieldNames.charAt(4)) == "f")
if (String(fieldNames.charAt(4)) == "f")
