从文本字段获取数值

Question

解决：我目前正在使用Netbeans（JFrames）编写程序，我需要使用'.get'之一从文本字段获取数值。

新问题：在执行contactumber的'if语句'时，给我一个错误，指出不能取消引用int。 有什么建议么 ？

    namevalidation.setText(""); //Set text for the label
    surnamevalidation.setText(""); //Set text for the label
    contactvalidation.setText(""); //Set text for the label

    String name = namefield.getText(); //Get text form a textfield
    String surname = surnamefield.getText(); //Get text form a textfield
    int contactnumber = Integer.parseInt(contactfield.getText()); //Getting the numeric value form the textfield


    boolean passed=true;

    if(name.isEmpty())//Checking if the name or surname is empty
    {
        namevalidation.setText("Please enter your name!");
        passed = false;
    }

    if(surname.isEmpty())
    {
        surnamefield.setText("Please enter your surname!");
        passed = false;
    }
    if(contactnumber.isEmpty()) //THIS IS GIVING ME AN ERROR
    {
        contactfield.setText("Please enter your number!");
        passed = false;
    }

Answer 1

您应该使用Integer#parseInt方法：

int contactnumber = Integer.parseInt(contactfield.getText());

Integer#parseInt接受一个String并将其转换为原始int如果它是有效数字）。 如果数字无效，则将引发NumberFormatException 。

说明文件Integer#parseInt ：

/**
 * Parses the string argument as a signed decimal integer. The
 * characters in the string must all be decimal digits, except
 * that the first character may be an ASCII minus sign {@code '-'}
 * ({@code '\u005Cu002D'}) to indicate a negative value or an
 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 * indicate a positive value. The resulting integer value is
 * returned, exactly as if the argument and the radix 10 were
 * given as arguments to the {@link #parseInt(java.lang.String,
 * int)} method.
 *
 * @param s    a {@code String} containing the {@code int}
 *             representation to be parsed
 * @return     the integer value represented by the argument in decimal.
 * @exception  NumberFormatException  if the string does not contain a
 *               parsable integer.
 */

Answer 2

最简单的方法是将其获取为String并使用Integer.parseInt()方法转换为数字。

String contactNumberStr = contactfield.get();

if (contactNumberStr != null) {
    try {
        int contactNumber = Integer.parseInt(contactNumberStr);
    } catch (NumberFormatException e) {
        // contactfield is not having a number
    }
}