????int?i=0;
		????int?j=0;
			String?str="want?you?to?know?one?thing";
			for(i=0;i<str.length();i++){
					if(str.charAt(i)=='n'){
						j++;
					}
				}
			System.out.print(j);

String?str?=?"want?you?know?one?thing";
		int?num=0;
		for(int?i=0;?i<str.length();?i++){
			if(str.charAt(i)?==?'n'){
				num++;
			}
		}
		System.out.println(num);

。。。哥們。。。作業的話自己做一做領悟得更深一些吧。。直接要代碼對自己的學習一點也不好。。。你可以多問問細節。。

String?str?=?"want?you?to?know?one?thing";
int?n?=?'n';
char?[]?chars?=?str.toCharArray();
int?count?=?0;
for?(int?i?=?0;i?<?chars.length;i++){
????if((int)chars[i]?==?n){
????????count?++;
????}
}

親測可用

String ss = "want you to know one thing";
?? ??? ?byte[] ssb= ss.getBytes();
?? ??? ?byte[] s = "n".getBytes();
?? ??? ?int i = 0;
?? ??? ?for (byte b : ssb) {
?? ??? ??? ?if(b == s[0]){
?? ??? ??? ??? ?i++;
?? ??? ??? ?}
?? ??? ?}
?? ??? ?System.out.println(i);

String s= "want you to know one thing";

String[] ssss = s.split("n");

ssss 的長度-1；