Java 字符串分析：统计字母、数字和字符频率

public class Main {\n public static void main(String[] args) {\n String str = "AJFDOI987EQJF9Q7498OFJALKJF9Vmvaou809890q9jldaouq1100inbknvll";\n \n // 打印有多少个大写字母、小写字母、数字\n int uppercaseCount = 0;\n int lowercaseCount = 0;\n int digitCount = 0;\n for (int i = 0; i < str.length(); i++) {\n char c = str.charAt(i);\n if (Character.isUpperCase(c)) {\n uppercaseCount++;\n } else if (Character.isLowerCase(c)) {\n lowercaseCount++;\n } else if (Character.isDigit(c)) {\n digitCount++;\n }\n }\n System.out.println("大写字母个数：" + uppercaseCount);\n System.out.println("小写字母个数：" + lowercaseCount);\n System.out.println("数字个数：" + digitCount);\n \n // 打印有多少个不同的字符\n int distinctCount = 0;\n boolean[] visited = new boolean[256];\n for (int i = 0; i < str.length(); i++) {\n char c = str.charAt(i);\n if (!visited[c]) {\n distinctCount++;\n visited[c] = true;\n }\n }\n System.out.println("不同字符个数：" + distinctCount);\n \n // 打印有多少个A\n int aCount = 0;\n for (int i = 0; i < str.length(); i++) {\n if (str.charAt(i) == 'A') {\n aCount++;\n }\n }\n System.out.println("A的个数：" + aCount);\n \n // 打印每个字符的个数\n int[] count = new int[256];\n for (int i = 0; i < str.length(); i++) {\n char c = str.charAt(i);\n count[c]++;\n }\n for (int i = 0; i < count.length; i++) {\n if (count[i] > 0) {\n System.out.println((char)i + "的个数：" + count[i]);\n }\n }\n }\n}