Checking if a number is an Integer in Java

Question

Is there any method or quick way to check whether a number is an Integer (belongs to Z field) in Java?

I thought of maybe subtracting it from the rounded number, but

Answer 1

With Z I assume you mean Integers , i.e 3,-5,77 not 3.14, 4.02 etc.

A regular expression may help:

Pattern isInteger = Pattern.compile("\\d+");

Answer 2

Check if ceil function and floor function returns the same value

static boolean isInteger(int n) 
{ 
return (int)(Math.ceil(n)) == (int)(Math.floor(n)); 
} 

Answer 3

    double x == 2.15;

    if(Math.floor(x) == x){
        System.out.println("an integer");
    } else{
        System.out.println("not an integer");
    }

I think you can similarly use the Math.ceil() method to verify whether x is an integer or not. This works because Math.ceil or Math.floor rounds up x to the nearest integer (say y) and if x==y then our original `x' was an integer.

Answer 4

// in C language.. but the algo is same

#include <stdio.h>

int main(){
  float x = 77.6;

  if(x-(int) x>0)
    printf("True! it is float.");
  else
    printf("False! not float.");        

  return 0;
}

Answer 5

change x to 1 and output is integer, else its not an integer add to count example whole numbers, decimal numbers etc.

   double x = 1.1;
   int count = 0;
   if (x == (int)x)
    {
       System.out.println("X is an integer: " + x);
       count++; 
       System.out.println("This has been added to the count " + count);
    }else
   {
       System.out.println("X is not an integer: " + x);
       System.out.println("This has not been added to the count " + count);


   }