public class TestTemp {
    
    public static void main(String[] args) {
        double[] f = new double[20];
        f[0] = 2;
        f[1] = 3;
        double sum = 2/1 + 3.0/2;
        for(int i=2; i<20; i++) {
            f[i] = f[i-1]+f[i-2];
            sum += ((double)f[i]/(i+1));
        }

        System.out.println(sum);
    }
}

------解决方案--------------------
第一题http://topic.csdn.net/u/20110530/15/7648f8f0-e2e2-4a5b-a35d-8a1bbb43ac09.html

------解决方案--------------------

第2题，写了个组合的方法，LZ自己再写个字符串全排列输出就可以了：
Java code

public static void main(String[] args) {
        String[] ssss = {"a","b","c","d","e"};
        mm1(ssss);
    }

public static void mm1(String[] str) {
        for(int i = 1; i<=str.length;i++) {
            mm2(str,i,"");
            System.out.println();
        }
    }
    
    public static void mm2(String[] str,int n,String st) {
        if(str.length<n) {
            return;
        }
        else if(n==1) {
            String[] strr = new String[str.length];
            for(int i = 0; i<str.length;i++) {
                strr[i] = st+str[i];
                System.out.print(strr[i]+" ");
            }
        }
        else {
            String st2 = st+str[0];
            String[] str2 = new String[str.length-1];
            for(int i = 1; i <str.length;i++) {
                str2[i-1] = str[i];
            }
            mm2(str2,n-1,st2);
            mm2(str2,n,st);
        }
    }