Chapter II Fundamentals of Java language (2)

1. Write a Java application, find out e=1+1/1!+1/2!+1/3!+...+1/n!+ ... The approximate value, which requires less than 0.0001 error.

 Packagetest; Public classTest {//to find the factorial of n     Public Static intfnintN) {if(n = = 1)        {               return1; }          returnN*FN (n-1); }              //sum     Public Static DoubleSumintN) {Doublesum = 0;  for(; n!= 1; n--) {sum= Sum + (Double) 1/FN (n); //Be careful to convert to float or double .        }          returnsum; }       Public Static voidMain (String args[]) {intn = 10;     SYSTEM.OUT.PRINTLN (sum (n)); }    }

Output:

0.7182818011463845

2. Using variable column array to achieve multiplication formula printing

 Packagetest; Public classcfkj { Public Static voidMain (string[] args) {intArr[][] =New int[10] [10];  for(inti = 1;i<10;i++)        {             for(intj = 1;j<10;j++) {Arr[i][j]= i *J; }        }         for(inti = 1;i<10;i++)        {             for(intj = 1;j<10;j++) {System.out.print (i+ "x" +j+ "=" +arr[i][j] + "");        } System.out.println (); }    }}

Output:

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. Output graphics

 Packagetest; Public classPrint { Public Static voidMain (string[] args) {System.out.println ("*"); inti,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 (); }     }}

Output:

*
*.*.
*.. *.. *..
*...*...*...*...
*....*....*....*....*....
*.....*.....*.....*.....*.....*.....
*......*......*......*......*......*......*......
*.......*.......*.......*.......*.......*.......*.......*.......

Chapter II Fundamentals of Java language (2)