如何在Java中将字符串输入转换为双精度输入？[副本]

Question

我的代码不起作用，而且“checkValidNumber（瞬时值）”中有错误，表示字符串不能转换为double。

/**
 * Add a pokémonCard to collection
 */
public void addPokémonCard()
{
    final int INCREMENT = 1;
    
    boolean repeat = true;  // a boolean variable return true
    
    // Ask user for details
    String name = UI.askString("Name of PokémonCard: ");
    if (name.equals("")) {
        UI.println("I don't recognise that command");
        addPokémonCard();
    } else if (name == null ) {
        UI.println("Please type a PokémonCard's name: ");
        addPokémonCard();
    } else {
        // Check boundaries for the number of the momentary value of PokémonCard added
        do {
            String momentary_value = UI.askString("Momentary value: ");
            // Check a suitable value of a PokémonCard 
            if (checkValidNumber(momentary_value)){
                double momentary_value1 = Double.parseDouble(momentary_value);
                // Increment the PokémonCard ID count and add to hashmap
                pokémonCards.setPokémonCardId(); // Increment the id by 1
                //add a PokémonCard image to display in the GUI
                String imgFileName = UIFileChooser.open("Choose Image File: ");
                pokémonCards.addPokémonCard(name, momentary_value1, imgFileName);
                UI.println("Added");
                repeat = false;
            } else if (checkValidNumber(momentary_value) == false) { // Check for invalid value
                UI.println("Please input a valid price!");
            } else { // Check for invalid value
                UI.println("Must be a number!");
            }
        }while (repeat); //repeat the method again if there's null input
    }
}

/**
 * Check a valid number for momentary value
 * @return boolean false if it's an invalid number
 * @param momentary_value for the price of PokemonCard
 */
public boolean checkValidNumber(double momentary_value){
    boolean validNumber = false;
    if (momentary_value > 0) { 
        validNumber = true;
    } 
    return validNumber;
}

Answer 1

你需要先转换成双倍

checkValidNumber(Double.parseDouble(momentary_value))