用Java从键盘上输入一段中文组成的字符串，统计其中汉字个数。用三种方法

好的，下面是三种不同的方法来统计中文字符串中的汉字数量。

## 方法1：通过正则表达式匹配汉字

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入中文字符串：");
        String input = scanner.nextLine();

        // 使用正则表达式匹配汉字
        Pattern pattern = Pattern.compile("[\u4e00-\u9fa5]");
        Matcher matcher = pattern.matcher(input);

        // 统计汉字数量
        int count = 0;
        while (matcher.find()) {
            count++;
        }
        System.out.println("汉字数量：" + count);
    }
}

## 方法2：通过遍历字符串判断每个字符是否为汉字

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入中文字符串：");
        String input = scanner.nextLine();

        // 遍历字符串，判断每个字符是否为汉字
        int count = 0;
        for (int i = 0; i < input.length(); i++) {
            char c = input.charAt(i);
            if (isChinese(c)) {
                count++;
            }
        }
        System.out.println("汉字数量：" + count);
    }

    public static boolean isChinese(char c) {
        Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
        return ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A
                || ub == Character.UnicodeBlock.GENERAL_PUNCTUATION
                || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
                || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS;
    }
}

## 方法3：通过将字符串转化为字符数组，判断每个字符是否为汉字

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入中文字符串：");
        String input = scanner.nextLine();

        // 将字符串转化为字符数组，判断每个字符是否为汉字
        int count = 0;
        for (char c : input.toCharArray()) {
            if (isChinese(c)) {
                count++;
            }
        }
        System.out.println("汉字数量：" + count);
    }

    public static boolean isChinese(char c) {
        Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
        return ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A
                || ub == Character.UnicodeBlock.GENERAL_PUNCTUATION
                || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
                || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS;
    }
}

以上三种方法都可以用来统计中文字符串的汉字数量，您可以根据自己的需求选择其中一种。