java如何判斷一個字符串中某個字符有幾個

判斷長度

"abc".length()

判斷某個字du符有zhidao幾個

String a = "abbdfsads";

int n = a.length()-a.replaceAll("a", "").length();
System.out.println("字符串中zhuan字符a有"+n+"個");