Java get int from string input

You can use the combination of the functions to determine whether a string is an int or not

public boolean isInteger(String str) {
  try {
    Integer.parseInt(str);
    return true;
  } catch(NumberFormatException e) {
    return false;
  }
}

If this function returns true ... string is an integer ... now get the integer value using

Integer.parseInt(str);

First thing I want to note is that a String should not be compared with ==, rather you should use string.equals(comparedString); You can also use the following code to parse through all the inputs that a person enters, and then use both the string entered and the string value entered and it would not be dependent on the start of the string. This would satisfy the options for them all; insert, delete, ect.

String userInput;//received by system in
String choice;
int choiceInt;
for (int i = 0; i < userInput.length(); i++) 
{
    Character character = userInput.charAt(i);
    if (!Character.isDigit(character)) 
    {
        choice += character;
    }
    else if (Character.isDigit(character))
    {
        choiceInt += character;
    }
    else
    {
        System.out.println("Unable to determine character.");
    }

    /* Code for the comparison of String based option */
    //Example
    if (choice.equalsIgnoreCase("insert")//NOTE: the ignore case, 
                                         // you want users to be                        
                                         // able to enter in strings 
                                         // and not have a case sensitivity.
    {
        /* do the code you planned on doing here */
    }
}

You could also assign integer values for each String possibility that you are willing to accept as valid options. This would increase the coding but also would also for a switch case statement. (which is still interpreted as if, else if, else statements) I think at that point it would be more up to the developers intentions and design preferences. Please correct me if I am wrong.

You can also replace the final else statement by either using a try and catch block.

Try this:

if (input.startsWith("insert")) {
    int num = Integer.parseInt(input.replaceAll("\\D", ""));

}