10 - Looping 2

Experiments

Experiment 1

Create new class Star then save as Star.java
Add main() function inside the class
Because in the program we need input from user, add import Scanner at first line
```
import java.util.Scanner;
```

Declare object Scanner as scanner.

Scanner scanner = new Scanner(System.in);

In the next line, ask user to input the value of N

System.out.print("Input N: ");
int N = scanner.nextInt();

Add basic syntax loop using keyword for
```
for (int i = 1; i <= N; i++) {
  System.out.print("*");
}
```
Note: use print not println, because we need to display in single line without new line.
Compile then execute the program!
Make an observation, then check your result of program! Ensure your output the program like below.
```
Input N: 5
*****
```
Questions
What happen if the initial value i = 1 changed into i = 0? Explain your argument!
What happen if the condition i <= N changed into i > N? Explain your argument!
What happen if the statement i++ changed into i--? Explain your argument!

Experiment 2

In this experiment, we'll make nested loop program. We want to display square of star based on N value. If the value N is 5, the output program becomes:
```
*****
*****
*****
*****
*****
```
Create class Square and save as Square.java
Add statement in first line to import Scanner library
```
import java.util.Scanner;
```
Add main() function inside the class

Inside main() function, add same logic in the previous experiment.

Scanner scanner = new Scanner(System.in);
System.out.print("Input N: ");
int N = scanner.nextInt();
for (int i = 1; i <= N; i++) {
  System.out.print("*");
}

Compile and then execute the program. Ensure the output is equals like the previous experiment.

Check looping syntax in the previous step. The syntax display * as many as N times. We need to repeat that process, so one more looping is needed.

for (int iOuter = 1; iOuter <= N; iOuter++) {
  for (int i = 1; i <= N; i++) {
    System.out.print("*");
  }
  System.out.println();
}

Save, compile then execute the program!

Make an observation, test the program!

  Input N: 5
  *****
  *****
  *****
  *****
  *****

Questions

What happen if the initial value iOuter = 1 changed into iOuter = 0? Why?
Revert back the initial value iOuter = 1. Then change the initial value i = 1 in inner loop into i = 0. Make an observation and explain!
What the purpose of System.out.println();? Why we need this statement inside the program? What happen if the statement removed?
Modify the program to display triangle of star!
```
*
**
***
****
*****
```

Experiment 3

Create a new class Quiz and save as Quiz.java

import library Random and Scanner in the first line

  import java.util.Random;
  import java.util.Scanner;

Add main() function
Inside main() function, declare objects from Random and Scanner. Random class used to get a generate number.
```
  Random random = new Random();
  Scanner input = new Scanner(System.in);
```

In the next line, add syntaxes below

  char menu = 'y';
  do {
    int number = random.nextInt(10) + 1;
    boolean success = false;
    do {
      System.out.print("Guess a number (1 - 10): ");
      int answer = input.nextInt();
      input.nextLine();
      success = (answer == number);
    } while(!success);
    System.out.print("Do you want to try again (Y/y)?");
    menu = input.findInLine(".").charAt(0);
    input.nextLine();
  } while (menu == 'y' || menu == 'Y');

Note: Statement input.nextLine() used to skip new line input.

Compile then execute the program!

Questions

Explain the flow of program above!
Modify the program, add additional hint to guess a number. Display smaller or bigger based on the answer!

Assignment

(NumberTriangle) Create a program to display Number Triangle like below (row's value is 2 and 4)! The minimal of row's value is 1.
```
         1
        12
  1    123
 12   1234
```

(HourGlass) Create a program to display a hourglass based on the value of N! The minimal value of N is 2.

       *********
        *******
         *****
          ***
           *
          ***
 ***     *****
  *     *******
 ***   *********

 N=2     N=4

(SquaredNumber) Create a program to display square like below (row is 3 and 5)! The minimal value of row is 3.
```
       55555
       5   5
 333   5   5
 3 3   5   5
 333   55555
```
(OppositeNumber) Create a program to display opposite number like figure below! Row's value between 3 and 6.
```
         123456
         654321
         123456
 123     654321
 321     123456
 123     654321
```

(PineTree) Create a program to display pine tree like below (N is 2 and 3)! The minimal value of N is 2.

         *
        ***
       *****
         *
        ***
  *    *****
 ***     *
  *     ***
 ***   *****

(PrimeNumber) Display the prime number as many as N! The minimal value of N is 1.
```
N = 4
2 3 5 7

N = 1
2
```

10 - Looping 2

10 - Looping 2

Experiments

Experiment 1

Questions

Experiment 2

Questions

Experiment 3

Questions

Assignment

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