Table of Contents
In this article, we will write the Java programs to check if a number is positive or negative. We have used the following ways to check the number is positive, negative, or zero.
- Using Relational Operator
- Using Math.signum() Method
- Using Integer.signum() Method
- Using Bit Shift Operator
- Using ArrayList class
Using Relational Operator
To check the positive and negative of a number, we have implemented the following logic in the Java program
- If number>0 the number is positive.
- If number<0 the number is negative.
- If a number is neither positive nor negative, the number is equal to 0.
Let’s implement the above logic in a Java program using the if-else statement
In the following program, we have initialized a number and used the if-else statement to check if a number is positive or negative.
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CheckPositiveOrNegativeExample1.java
- public class CheckPositiveOrNegativeExample1
- {
- public static void main(String[] args)
- {
- //number to be check
- int num=912;
- //checks the number is greater than 0 or not
- if(num>0)
- {
- System.out.println(“The number is positive.”);
- }
- //checks the number is less than 0 or not
- else if(num<0)
- {
- System.out.println(“The number is negative.”);
- }
- //executes when the above two conditions return false
- else
- {
- System.out.println(“The number is zero.”);
- }
- }
- }
Output:
The number is positive.
In the following program, we have taken a number from the user and used the if-else statement to check if a number is positive or negative.
CheckPositiveOrNegativeExample2.java
- import java.util.Scanner;
- public class CheckPositiveOrNegativeExample2
- {
- public static void main(String[] args)
- {
- int num;
- //object of the Scanner class
- Scanner sc = new Scanner(System.in);
- System.out.print(“Enter a number: “);
- //reading a number from the user
- num = sc.nextInt();
- //checks the number is greater than 0 or not
- if(num>0)
- {
- System.out.println(“The number is positive.”);
- }
- //checks the number is less than 0 or not
- else if(num<0)
- {
- System.out.println(“The number is negative.”);
- }
- //executes when the above two conditions return false
- else
- {
- System.out.println(“The number is zero.”);
- }
- }
- }
Output 1:
Enter a number: 23 The number is positive.
Output 2:
Enter a number: -499 The number is negative.
Output 3:
Enter a number: 0 The number is zero.
Using Math.signum() Method
There is an alternate way to check if a number is positive or negative. Java Math class provides the signum() method to check if a number is positive or negative. It is a static method that accepts a parameter of double type.
Syntax:
- public static double signum(double d)
Where d is a parameter whose signum is to be returned. It returns the signum function of the argument, as follows:
0.0: if the argument is 0.
1.0: if the argument>0.
-1.0: if the argument<0.
Special Cases:
NaN: if the argument is NaN.
Argument: if the argument is positive or negative zero.
It is an overloaded method, so the Math class also provides a signum() method that accepts a float value to check if a number is positive or negative.
Syntax:
- public static float signum(float f)
Let’s use the signum() method in a Java program.
CheckPositiveOrNegativeExample3.java
- import java.util.Scanner;
- import java.lang.Math.*;
- public class CheckPositiveOrNegativeExample3
- {
- public static void main(String[] args)
- {
- double num, result;
- //object of the Scanner class
- Scanner sc = new Scanner(System.in);
- System.out.print(“Enter a number you want to check: “);
- //reading an input from the user
- num = sc.nextDouble();
- //invoking signum() method of the Math class
- result=Math.signum(num);
- //print the result
- System.out.print(result);
- }
- }
Output:
Enter a number you want to check: -98.6 -1.0
Using Integer.signum() Method
Java Integer class also provides the signum() method to check if a number is positive or negative. It is a static method that accepts a parameter of integer type.
Syntax:
- public static int signum(int i)
Where i is a parameter whose signum is to be returned. It returns the signum function of the argument, as follows:
the argument, as follows:
0: if the argument is 0.
1: if the argument>0.
-1: if the argument<0.
Let’s use the Integer.signum() method in a Java program.
CheckPositiveOrNegativeExample4.java
- import java.util.Scanner;
- import java.lang.Integer.*;
- public class CheckPositiveOrNegativeExample4
- {
- public static void main(String[] args)
- {
- int num, result;
- //object of the Scanner class
- Scanner sc = new Scanner(System.in);
- System.out.print(“Enter a number you want to check: “);
- //taking an integer value from the user
- num = sc.nextInt();
- //invoking signum() method of the Integer class
- result=Integer.signum(num);
- //prints the result
- System.out.print(result);
- }
- }
Output 1:
Enter a number you want to check: 99 1
Output 2:
Enter a number you want to check: -99 -1
Output 3:
Enter a number you want to check: 0 0
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Using Bit Shift Operator
In Java, the integers are stored in the 2’s complement. We know that the highest bit of any negative number is 1, and the highest bit of any other number is 0.
In the following program, the bit shift operator (num>>31) copies the highest bit to every other bit. Therefore, the negative number becomes 11111111 11111111 11111111 11111111, and the positive or zero numbers become 00000000 00000000 00000000 00000000. The operator & sets the lowest bit to 0. Hence, the combination of [(num >> 31) & 1] reads only the highest bit of num. Note that it considers 0 as a positive number.
CheckPositiveOrNegativeExample5.java
- import java.util.Scanner;
- public class CheckPositiveOrNegativeExample5
- {
- public static void main(String[] args)
- {
- int num, result;
- //object of the Scanner class
- Scanner sc = new Scanner(System.in);
- System.out.print(“Enter a number you want to check: “);
- //taking an integer value from the user
- num = sc.nextInt();
- //string array that contains results
- String[] result = {“Positive”, “Negative”};
- //checks if the number is positive or negative
- System.out.println(result [(num >> 31) & 1]);
- }
- }
Output 1:
Enter a number you want to check: -98 Negative
Output 2:
Enter a number you want to check: 0 Positive
Let’s see another logic to check if the number is positive or negative.
Using ArrayList Class
In the following example, we have created a static method named positiveOrNegative(). It accepts a parameter n of type int. We have created an object of ArrayList class for storing the result positive, negative, and zero. After that, a for loop is used that populates the ArrayList with elements Positive for n elements. If n is positive n will be the index in the ArrayList and return the element Positive as the result. If n is negative, it will never exist in an index of the ArrayList.
CheckPositiveOrNegativeExample6.java
- import java.util.*;
- public class CheckPositiveOrNegativeExample6
- {
- public static void main(String[] args)
- {
- //invoking method and prints the corresponding result
- //parsing a positive value as a parameter
- System.out.println(positiveOrNegative(42));
- //parsing zero as a parameter
- System.out.println(positiveOrNegative(0));
- //parsing a negative value as a parameter
- System.out.println(positiveOrNegative(-190));
- }
- //method to check if the number is positive or negative
- public static String positiveOrNegative(int n)
- {
- //object of the ArrayList class
- ArrayList<String> result = new ArrayList<String>();
- //if n is 0, the response is Zero
- //adds zero to the list
- result.add(“Zero”);
- //the loop populates the ArrayList with elements “Positive” for n elements
- for(int i=0; i<n; i++)
- {
- //adds result to the list
- result.add(“Positive”);
- }
- String result=“”;
- //try-catch block for the get() method because it throws IndexOutOfBoundsException
- try
- {
- //the get() method returns the element at the specified position in this list
- result=result.get(n);
- }
- catch (Exception e)
- {
- //if the index is out of bounds, it must be negative
- result=“Negative”;
- }
- //returns the result
- return result;
- }
- }
Output:
Positive Zero Negative
Let’s see another logic to check if the number is positive or negative.
CheckPositiveOrNegativeExample7.java
- public class CheckPositiveOrNegativeExample7
- {
- public static void main(String[] args)
- {
- System.out.println(positiveOrNegative(111));
- System.out.println(positiveOrNegative(-444));
- }
- //method to check the number positive or negative
- public static String positiveOrNegative(int n)
- {
- //array of result that contains string Negative, Zero, and Positive
- String[] results = {“Negative”, “Zero”, “Positive”};
- //logic to check if the number is positive or negative and return the string as result
- return results[1+(1+((n+1)%n)*((n-1)%n))/n];
- }
- }
Output:
Positive Negative
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In this article, we have discussed a lot of ways to check if a number is positive or negative. But we recommend you to use the relation operator to check the number is positive or negative.