From charlesreid1

Check if a string is numeric

To check if a String in Java is numeric, build a simple utility function:

public static boolean isNumeric(String str)  
        double d = Double.parseDouble(str);  
      catch(NumberFormatException nfe)  
        return false;  
    return true;  

Interpret character as digit

The Character class has the static digit method, which takes a character and an integer radix, and returns an integer - the character interpreted as an integer. It also has a boolean isDigit() to check if the character is a digit. Use them in combo:

		// Create a container of digit-characters
		String n = "2432902008176640000";
		char[] narr = n.toCharArray();

		// Populate a queue with characters
		Queue<Character> q = new LinkedList<Character>();
		for(int i=0; i<narr.length; i++) {

		// Print out the square of each character interpreted as a digit
		StringBuilder sb = new StringBuilder();

		int j = 0;
		for(Character c : q) {
		    int z = -10000;
			// Character.isDigit() and Character.digit() are static methods
		    if( Character.isDigit(c) ) {
		        z = Character.digit(c,10);
			if(j<q.size()-1) {
		    	    sb.append(", ");
		    } else {
		        throw new IllegalArgumentException("Malformed input. Numeric strings only.");



See also: