1. Java Basics (personal Summary) (4)

14.for Loop output Yang Hui's triangle

The Yang Hui's triangle is a numerical arrangement, and we can consider it as a numeric table whose basic properties are the sum of the digits on both sides of the value 1, the number at the other position, and the value of the upper left.

int [] [] triangle=new int[8][];

for (int i=0;i<triangle.length;i++) {//Row control

triangle[i]=New int[i+1];//declares a one-dimensional array for each row

for (int j=0;j<triangle[i].length;j++) {//Column control

if (i==0| | j==0| | J==TRIANGLE[I].LENGTH-1) {

Triangle[i][j]=1;

}Else{

TRIANGLE[I][J]=TRIANGLE[I-1][J]+TRIANGLE[I-1][J-1];

}

Output array element

System. out. Print (triangle[i][j]+ "\ t");

}

System. out. println ();

}

Results:

1

1 1

1 2 1

1 3 3 1

1 4 6 4 1

1 5 10 10 5 1

1 6 15 20 15 6 1

1 7 21 35 35 21 7 1

Note: The two-dimensional array in the Java language is actually a one-dimensional array of each element is another one-dimensional array, so the length of the second array can be arbitrary. 15.for Loop implementation 99 multiplication table

for (int i=0;i<9;i++) {//Row control

for (int j=0;j<=i;j++) {//Line control System. out. Print ((j+1) + "*" + (i+1) + "=" + (j+1) * (i+1) + "T");

}

System. out. println ();

}

The results are:

1*1=1

1*2=2 2*2=4

1*3=3 2*3=6 3*3=9

1*4=4 2*4=8 3*4=12 4*4=16

1*5=5 2*5=10 3*5=15 4*5=20 5*5=25

1*6=6 2*6=12 3*6=18 4*6=24 5*6=30 6*6=36

1*7=7 2*7=14 3*7=21 4*7=28 5*7=35 6*7=42

1*8=8 2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64

1*9=9 2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81 16.for loop output Hollow Diamond

if (size%2==0) {

size++; Calculate the size of a diamond

}

for (int i=0;i<size/2+1;i++) {

for (int j=size/2+1;j>i+1;j--) {

System. out. Print ("");//output blank in upper left corner

}

for (int j=0;j<2*i+1;j++) {

if (j==0| | J==2*i) {

System. out. Print ("*");//output diamond upper half Edge

}Else{

System. out. Print ("");//output diamond Upper half Hollow

}

}

System. out. println ();

}

for (int i=size/2+1;i<size;i++) {

for (int j=0;j<i-size/2;j++) {

System. out. Print ("");//output diamond lower left corner blank

}

for (int j=0;j<2*size-1-2*i;j++) {

if (j==0| | j==2* (size-i-1)) {

System. out. Print ("*");//output diamond bottom half edge

}Else{

System. out. Print ("");//output diamond bottom half hollow

}

}

System. out. println ();

}

Set the size to 7, the result is:

*

* *

*   *

*    *

*   *

* *

*

17. Calculation of 1+1/2!+1/3!...... 1/20!

int I=1;

BigDecimal sum=New BigDecimal (0.0);

BigDecimal temp=New BigDecimal (1.0);

while (I<=20) {

Temp=temp.multiply (new BigDecimal (1.0/i));//Calculate factorial item

Sum=sum.add (temp);//Add the sum of the factorial

i++;

}

System. out. println ("1+1/2!+1/3!...... 1/20!= "+sum);

The results are:

1+1/2!+1/3!...... 1/20!=1.7182818284 ...