如何统计字符串中某字符的个数

如何统计字符串中某字符的个数

public class StrTest {
public static int f(String s1,String s2){
int a = s1.length();
int b = s2.length();
int i = 0,sum = 0;
while( i <= (b - a)){
if(s1.charAt(0) == s2.charAt(i)){
if(s2.substring(i, i + a ).equals(s1))
{i = i + a - 1 ;
    sum++;
}
}
++i;
}
return sum;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("输入子字符串");
String s1 = sc.next();
System.out.println("输入母字符串");
String s2 = sc.next();
System.out.println("子字符串在母字符串中出现的次数是：" + f(s1,s2));
}

}

String str = "abcde123" ; int count = 0 ; for (int i = 0;i<str.length();i++){ if(str.substring(i,i+1).equals("a")){ count++; } } System.out.println(count);

private sub command1_click() dim w as integer, n as integer, t as integer '我你他的个数 for i = 1 to len(text1) select case mid(text1, i, 1) case "我" w = w + 1 case "你" n = n + 1 case "他" t = t + 1 end select next text2 = "我" & w & "个，你" & n & "个，他" & t & "个" end sub