1.编写一个java application,求出e=1+1/1!+1/2!+1/3!+...+1/n!+...的近似值,要求误差小于0.0001。
package test;public class Test { //求n的阶乘 public static int fn(int n) { if(n == 1) { return 1; } return n*fn(n-1); } //求和 public static double sum(int n) { double sum = 0; for(; n!= 1; n--) { sum = sum + (double)1/fn(n); //注意要强制转换成float或者double } return sum; } public static void main(String args[]) { int n = 10; System.out.println(sum(n)); } }
输出：
0.7182818011463845
2.利用可变列数组实现乘法口诀打印
package test;public class cfkj { public static void main(String[] args) { int arr[][] = new int[10][10]; for(int i = 1;i<10;i++) { for(int j = 1;j<10;j++) { arr[i][j] = i * j; } } for(int i = 1;i<10;i++) { for(int j = 1;j<10;j++) { System.out.print(i+"x"+j+"="+arr[i][j] + " "); } System.out.println(); } }} 输出：
1x1=1 1x2=2 1x3=3 1x4=4 1x5=5 1x6=6 1x7=7 1x8=8 1x9=9
2x1=2 2x2=4 2x3=6 2x4=8 2x5=10 2x6=12 2x7=14 2x8=16 2x9=18 3x1=3 3x2=6 3x3=9 3x4=12 3x5=15 3x6=18 3x7=21 3x8=24 3x9=27 4x1=4 4x2=8 4x3=12 4x4=16 4x5=20 4x6=24 4x7=28 4x8=32 4x9=36 5x1=5 5x2=10 5x3=15 5x4=20 5x5=25 5x6=30 5x7=35 5x8=40 5x9=45 6x1=6 6x2=12 6x3=18 6x4=24 6x5=30 6x6=36 6x7=42 6x8=48 6x9=54 7x1=7 7x2=14 7x3=21 7x4=28 7x5=35 7x6=42 7x7=49 7x8=56 7x9=63 8x1=8 8x2=16 8x3=24 8x4=32 8x5=40 8x6=48 8x7=56 8x8=64 8x9=72 9x1=9 9x2=18 9x3=27 9x4=36 9x5=45 9x6=54 9x7=63 9x8=72 9x9=81
3. 输出图形
package test;public class print { public static void main(String[] args) { System.out.println("*"); int i,j,k; for(i=2;i<=8;i++) { j=i; while(j>0) { k=i-1; System.out.print("*"); while(k>0) { System.out.print("."); k--; } j--; } System.out.println(); } }} 输出：
*
*.*.*..*..*..*...*...*...*...*....*....*....*....*....*.....*.....*.....*.....*.....*.....*......*......*......*......*......*......*......*.......*.......*.......*.......*.......*.......*.......*.......