check if String is an integer?

[McChill]

Is there a method to check if a String is an integer? For example, I want to take the derivative of a term.

String term = args[0];

I assign the first command line to a String called term. Then I want to check if the first index of the string is a number with an if statement. But I can't figure out a way to check "is the first index in this string a whole number?" I was thinking

if(term.startsWith()...

but i dont know how to check if it starts with a whole number. can anyone help me please?

[OrangeDog]

String.matches() to check format of string
Scanner to parse a command line
Integer.parseInt() to convert string to int

[McChill]

Okay well my whole program turned out to look like this

import java.util.Scanner;
public class Derivative {
	
	private int power;
	private int coefficient;
	private String variable;
	
	public static void main(String args[]) {
		Derivative d = new Derivative();
		System.out.println(d.getDerivative(args[0])); 	//LINE 10
		
	}

	public void setPower(int power) {
		this.power = power;
	}

	public int getPower() {
		return power;
	}

	public void setCoefficient(int coefficient) {
		this.coefficient = coefficient;
	}

	public int getCoefficient() {
		return coefficient;
	}

	public void setVariable(String variable) {
		this.variable = variable;
	}

	public String getVariable() {
		return variable;
	}
	
	public String getDerivative(String term)
	{
		String derivative;
		Scanner scanner = new Scanner(term);	//pass the term to the scanner
		setCoefficient(scanner.nextInt());		//set the coefficient as the first integer	LINE 42	
		setVariable(scanner.next());			//set the variable as the next term after first integer
		setPower(scanner.nextInt());			//set the exponent power as the second integer
		int newCoefficient = power * coefficient;	//differentiate
		int newPower = power - 1;
		derivative = coefficient + variable + "^" + power;	
		return derivative;
		
	}
}

When i run it, I get the following message --
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at Derivative.getDerivative(Derivative.java:42)
at Derivative.main(Derivative.java:10)

I'm unsure what it is trying to tell me other than something is wrong with line 42 and line 10. What is another way I can assign the coefficient variable to the first integer value in the String? Or could you point me in the right direction? Thanks.

[angryboy]

in dos, you need to use:
java Derivative "1 2 3"
and NOT
java Derivative 1 2 3

because 1 is args[0]
2 = args[1]
and so on...

[OrangeDog]

InputMismatchException: The input wasn't what the scanner was expecting. You told it to nextInt() but the next token wasn't an integer.

[McChill]

awesome! thanks!