### Similar Tutorials

# Read input Until Negative Number is Entered

Loops are usually prepared to run a certain number of times. One way to ensure that the user can enter as many numbers as he/she wants each time the program runs is to establish a loop that continues to receive input until a negative number is written.

24 March 2020 0 Java**Example 1:** Create a while loop and set user input as loop condition. We can also find the sum of the numbers entered by the user..

```
Scanner scanner = new Scanner(System.in);
System.out.println("Please enter a positive number. Or enter a negative number to exit the program");
int input = scanner.nextInt();
int sum = 0;
while(input >= 0)
{
sum += input;
System.out.println("Please enter a positive number. Or enter a negative number to exit the program");
input=scanner.nextInt();
}
System.out.println("Sum of the numbers you entered = " + sum);
```

**Console Output:**

Please enter a positive number. Or enter a negative number to exit the program

4

Please enter a positive number. Or enter a negative number to exit the program

116

Please enter a positive number. Or enter a negative number to exit the program

25

Please enter a positive number. Or enter a negative number to exit the program

0

Please enter a positive number. Or enter a negative number to exit the program

99

Please enter a positive number. Or enter a negative number to exit the program

-1

Sum of the numbers you entered = 244

**Example 2:** Let's prepare the same example with for loop. Since the second parameter of the for loop is the loop consition, we can use the for loop in a different way

```
Scanner scanner = new Scanner(System.in);
int sum = 0;
int input=0;
for (int i=0; input>=0; i++)
{
System.out.println("Please enter a positive number. Or enter a negative number to exit the program");
input=scanner.nextInt();
sum += input;
}
System.out.println("Sum of the numbers you entered = " + sum);
```

**Console Output:**

Please enter a positive number. Or enter a negative number to exit the program

4

Please enter a positive number. Or enter a negative number to exit the program

5

Please enter a positive number. Or enter a negative number to exit the program

9

Please enter a positive number. Or enter a negative number to exit the program

116

Please enter a positive number. Or enter a negative number to exit the program

0

Please enter a positive number. Or enter a negative number to exit the program

44

Please enter a positive number. Or enter a negative number to exit the program

-1

Sum of the numbers you entered = 177

**Example 3:** Let's solve the same example with for loop and break statement.

```
Scanner scanner = new Scanner(System.in);
int sum = 0;
int input=0;
for (int i=0; i >= 0; i++) //endless loop
{
System.out.println("Please enter a positive number. Or enter a negative number to exit the program");
input=scanner.nextInt();
if (input<0)
break;
sum += input;
}
System.out.println("Sum of the numbers you entered = " + sum);
```

**Console Output:**

Please enter a positive number. Or enter a negative number to exit the program

44

Please enter a positive number. Or enter a negative number to exit the program

511

Please enter a positive number. Or enter a negative number to exit the program

0

Please enter a positive number. Or enter a negative number to exit the program

999

Please enter a positive number. Or enter a negative number to exit the program

-1

Sum of the numbers you entered = 1554