# Java: Display a three-digit number using 1, 2, 3, 4

## Java Basic: Exercise-39 with Solution

Write a Java program to create and display a unique three-digit number using 1, 2, 3, 4. Also count how many three-digit numbers are there.

**Pictorial Presentation:**

**Sample Solution:**

**Java Code:**

```
import java.util.Scanner;
public class Exercise39 {
public static void main(String[] args) {
int amount = 0; // Initialize a counter for three-digit numbers
// Iterate through three nested loops to generate all unique three-digit numbers
for (int i = 1; i <= 4; i++) {
for (int j = 1; j <= 4; j++) {
for (int k = 1; k <= 4; k++) {
// Check if 'i,' 'j,' and 'k' are all different (not equal)
if (k != i && k != j && i != j) {
amount++; // Increment the counter
System.out.println(i + "" + j + "" + k); // Print the generated three-digit number
}
}
}
}
// Display the total number of generated three-digit numbers
System.out.println("Total number of the three-digit-number is " + amount);
}
}
```

**Explanation:**

In the exercise above -

- First, the variable 'amount' is initialized to 0. This variable will be used to count the total number of three-digit numbers that meet the criteria.
- The code uses three nested for loops to generate all possible combinations of three digits from 1 to 4.
- The outermost loop iterates through the first digit (i) from 1 to 4.
- The middle loop iterates through the second digit (j) from 1 to 4.
- The innermost loop iterates through the third digit (k) from 1 to 4.
- Within the innermost loop, there is a conditional check if(k != i && k != j && i != j). This condition ensures that 'i', 'j', and 'k' are all distinct digits, meaning they are not equal to each other. This avoids repetition in the generated numbers.
- When a valid combination is found (i.e., three distinct digits), it increments the amount variable, prints the three-digit number in the format 'ijk', and moves on to the next combination.
- Finally, all possible combinations are generated and counted, it prints the total number of three-digit numbers that meet the criteria.

Sample Output:

123 124 132 134 142 143 213 214 231 234 241 ------ 431 432 Total number of the three-digit-number is 24

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