算法3-递归

/**
 * 时间:2010-02-07
 * @author 朴海林
 * 
 * 递归函数
 */
import java.io.*;

public class Recursive {

	public static void main(String[] args) {
		File f = new File("E:/Java Application");
		viewFile(f, 0);
		System.out.println(fibonacci(3));
		System.out.println(method(10));
		System.out.println(isHuiWen("aba"));
	}

	// 打印指定文件夹下的所有文件
	// 参数是文件和文件的等级
	private static void viewFile(File f, int level) {
		String str = "";
		File[] fs = f.listFiles();
		for (int i = 0; i < fs.length; i++) {
			str = "";
			for (int j = 0; j < level; j++) {
				str = str + "  ";
			}
			System.out.println(str + fs[i].getName());
			if (fs[i].isDirectory()) {
				viewFile(fs[i], level + 1);
			}
		}
	}

	// Fibonacci,菲波拉契数列
	private static int fibonacci(int f) {
		if (f <= 0) {
			return 0;
		}
		if (1 == f || 2 == f) {
			return 1;
		}else
		{
			return fibonacci(f - 1) + fibonacci(f - 2);
		}

	}

	//计算n!
	public static int method(int n) {
		if (n == 1) {
			return 1;
		} else {
			return n * (method(n - 1));
		}
	}

	//计算回文
	public static boolean isHuiWen(String s) {
		if (s == null) {
			return false;
		}
		if (s.length() == 0 || s.length() == 1) {
			return true;
		}
		char first = s.charAt(0);
		char last = s.charAt(s.length() - 1);
		if (first != last) {
			return false;
		} else {
			return isHuiWen(s.substring(1, s.length() - 1));
		}
	}
}