# 2: Loops

## 2.1 1 to 10

Write a method that prints the numbers 1 to 10

#### 2.1.1 Example

1:  oneToTen()
2:   *** Output ***
3:  1
4:  2
5:  3
6:  4
7:  5
8:  6
9:  7
10:  8
11:  9
12:  10

### 2.2 Odd Numbers

Write a method that prints the positive odd numbers less than 20

#### 2.2.1 Example

1:  oddNumbers()
2:   *** Output ***
3:  1
4:  3
5:  5
6:  7
7:  9
8:  11
9:  13
10:  15
11:  17
12:  19

### 2.3 Square Numbers

Write a method that prints the square numbers up to 100

#### 2.3.1 Example

1:  squares()
2:   *** Output ***
3:  1
4:  4
5:  9
6:  16
7:  25
8:  36
9:  49
10:  64
11:  81
12:  100

### 2.4 Random Numbers

Write a for loop to print out four random integers between 1 and 10

#### 2.4.1 Example

1:  random4()
2:   *** Output ***
3:  3
4:  5
5:  2
6:  8

### 2.5 Even Numbers < n

Write a method to print out the positive even numbers less than n

#### 2.5.1 Example

1:  even(20)
2:   *** Output ***
3:  2
4:  4
5:  6
6:  8
7:  10
8:  12
9:  14
10:  16
11:  18

### 2.6 Powers of 2

Write a method to print out the powers of 2 from 21 up to 2n

#### 2.6.1 Example

1:  powers(8)
2:   *** Output ***
3:  2
4:  4
5:  8
6:  16
7:  32
8:  64
9:  128
10:  256

### 2.7 Are we there yet?

Write a program that outputs “Are we there yet?” and then waits for input. If the input is “Yes” the program outputs “Good!” and exits, otherwise the program loops.

#### 2.7.1 Example

1:  "Are we there yet?"
2:  No
3:  "Are we there yet?"
4:  Spoons
5:  "Are we there yet?"
6:  Yes
7:  Good!

### 2.8 Triangle

Write a method that uses nested loops to produce the following pattern

1:  triangle()
2:   *** Output ***
3:  *
4:  **
5:  ***
6:  ****
7:  *****

### 2.9 Table Square

Write a method that prints out a 4 x 4 table square

#### 2.9.1 Example

1:  tableSquare()
2:   *** Output ***
3:  A 4 x 4 table square
4:  | 1 | 2 |  3 |  4 |
5:  | 1 | 2 |  3 |  4 |
6:  | 2 | 4 |  6 |  8 |
7:  | 3 | 6 |  9 | 12 |
8:  | 4 | 8 | 12 | 16 |

### 2.10 Table Squares

Extend your answer to the last question produce a method that will print out a n x n table square

#### 2.10.1 Example

1:  tableSquares(6)
2:   *** Output ***
3:  A 6 x 6 table square
4:  | 1 |  2 |  3 |  4 |  5 |  6 |
5:  | 2 |  4 |  6 |  8 | 10 | 12 |
6:  | 3 |  6 |  9 | 12 | 15 | 18 |
7:  | 4 |  8 | 12 | 16 | 20 | 24 |
8:  | 5 | 10 | 15 | 20 | 25 | 30 |
9:  | 6 | 12 | 18 | 24 | 30 | 36 |

1. Colin Richardson says:

I read that as “Two Loops”.. and not “2: Loops”
Thought it was an exercise in writing two concurrent loops (maybe using Threads).. I was quite impressed for a second.

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Ooh! Good point, I’ll change that. Threads come later… Any other feedback gratefully received!

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2. Max Roberts says:

Great Exercise for practising loops! It’s good to check you can still do the basics.

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3. blekdushi says:

above exercises are also good for practicing streams

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4. blekdushi says:

Example 2.7.1 is the only one to break with the “write a method…*** Output ***” pattern. Not sure if this is intended.

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