练习一

练习一：

package com.zy.test;

import java.util.Scanner;

public class test0 {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		System.out.print("two.in:\t");
		String Num = scanner.nextLine();
		// 通过空格分割字符串
		String[] temp = Num.split("\\s+");

		String c1 = temp[0];
		String c2 = temp[1];

		// String转int,用Integer里的ParseInt方法
		int startNum = Integer.parseInt(c1);
		int endNum = Integer.parseInt(c2);

		int m = 0;
		for (int i = startNum; i <= endNum; i++) {

			// int转String,用Integer里的toString方法
			String num = Integer.toString(i);
			// toCharArray()方法将字符串对象String转字符数组char[]
			char[] str1 = num.toCharArray();

			int n = 0;
			for (int j = 0; j < str1.length; j++) {
				if ('2' == str1[j]) {
					n++;
				}
			}

			m = m + n;
		}

		System.out.print("two.out:");
		System.out.println(m);
	}

}