斐波那契数列

public class Test {
	public static void main(String[] args) {
		int num1 = 1;
		int num2 = 1;
		int n = 2;
		int num3 = 1;
		long startTime = System.currentTimeMillis();
		for(int i = 3; i<=n;i++) {
			num3 = num1 + num2;
			num1=num2;
			num2=num3;
		}
		long endTime = System.currentTimeMillis();
		System.out.println(startTime - endTime);
		System.out.println("使用循环" + num3);
		
		startTime = System.currentTimeMillis();
		int result = fi(n);
		endTime = System.currentTimeMillis();
		System.out.println(startTime - endTime);
		System.out.println(result);
	}		
	public static int fi(int n) {
		int result = 0;
		if(n ==1 || n ==2) {
			result =1;	
		}else {
			result = fi(n-1)+ fi(n-2);
		}
		return result;
	}

}

代码进一步修改完善

public class Test {
	public static void main(String[] args) {
		int n = 5;

		long startTime = System.currentTimeMillis();
		System.out.println("使用循环" + f(n));
		long endTime = System.currentTimeMillis();
		System.out.println(startTime - endTime);

		startTime = System.currentTimeMillis();
		System.out.println(fi(n));
		endTime = System.currentTimeMillis();
		System.out.println(startTime - endTime);
	}	
	
	public static long f(int n) {
		if(n < 1) {
			System.out.println("有错误");
			return -1;
		}		
		long num1 = 1L;
		long num2 = 1L;
		long num3 = 1L;		
		
		if(n ==1 || n ==2) {
			num3 =1;	
		}		
		for(int i = 3; i<=n;i++) {
			num3 = num1 + num2;
			num1=num2;
			num2=num3;
		}		
		return num3;
	}
	
	
	public static long fi(int n) {
		if(n < 1) {
			System.out.println("有错误");
			return -1;
		}		
		long result = 0;
		if(n ==1 || n ==2) {
			result =1;	
		}else {
			result = fi(n-1)+ fi(n-2);
		}
		return result;
	}

}

下面的，我写了，一半

有需要的可以动动脑筋练练手

public class FiBoClass {
// 1、   1、    2、  3、5、8、13、21、34
//num1  num2  num3
	public static void main(String[] args) {
		int num1 = 1;
		int num2 = 1;
		int n = 9;
		int num3 = 0;
		for(int i=3; i<=n; i++) {
			num3 = num1 + num2;
			System.out.println("第"+i+"项的数字是：-->"+num3);
			num1 =num2;
			num2 = num3;
		}
		System.out.println(num3);
			
	}

}