Java charAt 错误“char 无法转换为字符串”
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charAt error "char cannot be converted to string"
提问by Hugo Pakula
I am trying to use the following code so that given a string, give the length of the longest contiguous subsequence of the same character. I am getting the error "incompatible types: char cannot be converted to java.lang.String". I have commented where the error is being found below.
我正在尝试使用以下代码，以便给定一个字符串，给出相同字符的最长连续子序列的长度。我收到错误“类型不兼容：char 无法转换为 java.lang.String”。我已经评论了下面发现错误的位置。
public class Test {
public int longestRep(String str)
{
int currLen = 1;
String currLet = "";
String maxLet = "";
int maxCount = 0;
int currPos = 0;
int strLen = str.length();
for(currPos = 0; currPos < strLen; currPos++)
{
currLet = str.charAt(currPos); //error is on this line
if(currLet = str.charAt(currPos+1))
{
currLen++;
}
else
{
if(currLen > maxLen)
{
maxLen = currLen;
maxLet = currLet;
currLen = 1;
}
}
}
}
public static void main(String args[])
{
longestRep("AaaaMmm");
}
}
采纳答案by MadProgrammer
currLet = str.charAt(currPos);AStringvalue can't be assigned to achar, they are different types, apples and orangesif (currLet = str.charAt(currPos + 1)) {is actually an assignment (makecurrLetequal to the value ofstr.charAt(currPos + 1))if (currLen > maxLen) {-maxLenis undefined- You never
returnanything from the method...
currLet = str.charAt(currPos);甲String值不能被分配给一个char，它们是不同的类型，苹果和桔子if (currLet = str.charAt(currPos + 1)) {实际上是一个赋值（使currLet等于的值str.charAt(currPos + 1)）if (currLen > maxLen) {-maxLen未定义- 你永远不会
return从方法中得到任何东西......
Try changing:
尝试改变：
String currLet = "";to something more likechar currLet = '\0';andString maxLet = "";tochar maxLet = '\0';if (currLet = str.charAt(currPos + 1)) {to something likeif (currLet == str.charAt(currPos + 1)) {- Add
int maxLen = 0to your variable declerations (may be underint maxCount = 0)
String currLet = "";到更多的东西一样char currLet = '\0';，并String maxLet = "";以char maxLet = '\0';if (currLet = str.charAt(currPos + 1)) {像if (currLet == str.charAt(currPos + 1)) {- 添加
int maxLen = 0到您的变量声明中（可能在 下int maxCount = 0）
Now, based on your example code, public int longestRep(String str) {will need to be public static int longestRep(String str) {in order for you to call from you mainmethod...
现在，根据您的示例代码，您public int longestRep(String str) {需要public static int longestRep(String str) {从您的main方法中调用...
回答by Paul
String.charAt(int)returns a character. But currLetis of type String, so you can't assign a character. Use currLet = Character.toString(str.charAt(currPos));instead.
String.charAt(int)返回一个字符。但是currLet是 type String，所以你不能分配一个字符。使用currLet = Character.toString(str.charAt(currPos));来代替。
回答by ajb
As the compiler said, you can't convert a charto a String. If you have a charand you really want to convert it to a Stringof length 1, this will work:
正如编译器所说，您不能将 a 转换char为 a String。如果您有 achar并且您确实想将其转换String为长度为 1 的 a，则可以这样做：
String s = String.valueOf(c);
or
或者
String s = Character.toString(c);
However, if the character you're working with was obtained by charAt, another solution is to get rid of charAtand use substringto return a string of length 1:
但是，如果您正在使用的字符是由 获得的charAt，另一种解决方案是摆脱charAt并使用substring返回长度为 1 的字符串：
currLet = str.substring(currPos, currPos + 1);
回答by Dias
Easy way to convert Char to String
将字符转换为字符串的简单方法
Add an empty String to the start of expression, because adding char and String results into String.
将一个空字符串添加到表达式的开头，因为将 char 和 String 添加到 String 中。
Convert one char"" + 'a'
Convert multiple chars"" + 'a' + 'b'
转换一个字符"" + 'a'
转换多个字符"" + 'a' + 'b'
Converting multiple chars works because "" + 'a'is evaluated first.
If the ""were at the end instead you would get "195"
转换多个字符有效，因为"" + 'a'首先评估。
如果""是在最后，你会得到"195"
Remember that Java language guarantees (Java Language Specification, Java SE 7 Edition, section 15.12.4.2) that all arguments are evaluated from left to right (unlike some other languages, where the order of evaluation is undefined)
请记住，Java 语言保证（Java 语言规范，Java SE 7 版，第 15.12.4.2 节）从左到右评估所有参数（与某些其他语言不同，评估顺序未定义）
