java - 循环计算字符串中给定字符数的问题

Question

我必须使用提供的循环来计算字符“b”在字符串 FourthString 中出现的次数，并且由于某种原因它返回了错误的数字。我相信这与 if 条件有关，但我可能是错的。

任何帮助将不胜感激。

字符串:

String FourthString = "棒球棒";

它应该返回 3。

代码格式:

char target        ='b';                               
int  length        = fourthString.length( );               
int  count         = 0;                                
int  startNxtSrch  = 0;                                
int  foundAt       = 0;                               

while( ....... ) {
    foundAt = .......;
    if ( ....... ) {
        startNxtSrch = foundAt +1;
        count += 1;
    } else {
        startNxtSrch = length;
    }
}  
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n", 
                   count,
                   target );

我尝试返回的数字不正确:

int i = 0;

while( i < length ) {
    foundAt = startNxtSrch;
    if ( fourthString.indexOf('b', startNxtSrch) != -1 ) {
        startNxtSrch = foundAt + 1;
        count += 1;
        i++;
    } else {
        startNxtSrch = length;
        i++;
    }
}
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n", 
                   count,
                   target );

Answer 1

这将为您提供正确的字符数:

char target        = 'b';
int  length        = fourthString.length( );
int  count         = 0;
int  startNxtSrch  = 0;
int  foundAt       = 0;

while(startNxtSrch < length) {
    foundAt = fourthString.indexOf(target,startNxtSrch);
    if (foundAt>=0) {
        startNxtSrch = foundAt + 1;
        count += 1;
    } else {
        startNxtSrch = length;
    }
}
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n",
            count,
            target );