Java编程仅用于2的乘法表

Question

Multiplication table for 2 only

This is my code:

public class nest
{
    public static void main (String[] args)
    {
        for (int row=1; row<=5; row++)
        {
            for (int column=1; column<=10; column++)
            {
                System.out.print(row*++column +"\t");

            }
          System.out.println();
        }
    }
}

This is my target results:

2   4   6   8   10  
12  14  16  18  20  
22  24  26  28  30  
32  34  36  38  40  
42  44  46  48  50  

But I'm getting this:

2   4   6   8   10  
4   8   12  16  20  
6   12  18  24  30  
8   16  24  32  40  
10  20  30  40  50  

Help me please I'm still learning Java.

Answer 1

The trick here is in being able to articulate a formula for the value in each cell given a row and column index. Assuming we count both row and column starting from zero, then the formula is:

(2 + 10*row + 2*column)

This formula says that, starting with an initial value of 2, we increase by 10 moving down a row, and we increase by 2 moving to the right of a column. This leads to the following code:

for (int row=0; row < 5; ++row) {
    for (int column=0; column < 5; column++) {
        System.out.print((2 + 10*row + 2*column) + "\t");
    }
      System.out.println();
}

Demo

Answer 2

To make it simple you can do something like this:

    public class A{

   public static void main(String[] args){
       int k=2;
      for (int row=1; row<=5; row++)
               {
                   for (int column=1; column<=5; column++)
                   {
                       System.out.print(k+"\t");
k=k+2;
                   }
                 System.out.println();
               }
           }
       }

Answer 3

Similar to the above one. A simple one.

public static void main(String[] args) {
    int tableOf = 2;
    int currIter = tableOf;
    for(int i = 1; i <= 5 ; i++) {
        currIter = tableOf * i;
        for(int j = 1; j <= 5 ; j++) {
            System.out.print((currIter * j) + "\t");
        }
        System.out.println();
    }
}

Answer 4

You can achieve your results by using an extra variable.

public class nest
{
public static void main (String[] args)
{ int table= 0;
    for (int row=1; row<=5; row++)
    {
        for (int column=1; column<=5; column++)
        {
            table+=2;
            System.out.print(table +"\t");

        }
      System.out.println();
    }
}
}

the loops can be used to define rows and columns for printing table . hope it helped you a little.

Answer 5

You could also try (assuming you're using Java 8+), a formula based on breaking lines every five elements using a lambda and a ternary we can do so in a single statement. Generate a range of 1 to 25, multiply each value in the range by 2, and then print it (and if it isn't a multiple of 5 a tab, otherwise a newline). Like,

IntStream.rangeClosed(1, 25).map(i -> i * 2)
        .forEachOrdered(i -> System.out.print(i + ((i % 5 != 0) ? "\t" : "\n")));

Answer 6

Your java code is great! It appears that you're just having a little bit of math logic problems.

Lets take a look at the following:

 1 2 3 4 5
1
2
3
4
5

These are your rows and columns as you itterate through them in your loops.

2 4 6 8 10

Should be your first line which it is!

12 14 16 18 20

Should be your second line. Well lets take a look at your equation.

row*++column

++column means column + 1 = 2

1 * 2 is 2

we want 12

If we keep the range of the loops within 5 its much simpler.

public class nest
{
    public static void main (String[] args)
    {
        for (int row=1; row<=5; row++)
        {
            for (int column=1; column<=5; column++)
            {
                System.out.print(logic math stuff +"\t");

            }
          System.out.println();
        }
    }
}

Looking at the expected output the numbers are just 1 - 25 * 2

Lets try to print 1 - 25 first.

Column itterates 1 - 5 so the first row is just column.

System.out.print(column + "\t");

1 2 3 4 5

Easy enough. So now on the second row we need 6 7 8 9 10.

Column is still 1 - 5 but row is now 2

The first number is supposed to be 6 so how do we get there?

row = 2 column = 1

Our column width is 5 so every itteration of row we have to add 5 * (row-1).

System.out.print((column + 5 * (row-1)) + "\t");

This prints 1 - 25 in 5 rows

Now double it!

System.out.print((column + 5 * (row-1)) * 2 + "\t");