Question

以下一些java课程初学者水平，进入了这个问题：

Multiple markers at this line
    - Syntax error on token "showMessageDialog", invalid 
     AnnotationName
    - Syntax error on token "(", { expected after this token
    - Syntax error on tokens, ConstructorHeaderName expected instead

，该行是：

JOptionPane.showMessageDialog(null, "The answer is " +sum, "The Title", JOptionPane.INFORMATION_MESSAGE);

Java Docs说这个方法接受4个参数，所以我发送4个参数。我也导入了所需的库：

import javax.swing.JOptionPane;

JOptionPane.showInputDialog工作正常，但不是JOptionPane.showMessageDialog。我错过了什么？谢谢。

完整代码

package java_practice;
import javax.swing.JOptionPane;

public class GraphicalUserInterface {
    String first_number = JOptionPane.showInputDialog("Enter first number");
    String second_number = JOptionPane.showInputDialog("Enter second number");

    int num1 = Integer.parseInt(first_number);
    int num2 = Integer.parseInt(second_number);
    int sum = num1 + num2;

    JOptionPane.showMessageDialog(null, "The answer is " +sum, "The Title", JOptionPane.INFORMATION_MESSAGE);
}

Answer 1

您错过了方法声明。您的代码位于类的主体内部，这会使编译器/ IDE混淆，例如，关于无效注释的错误等。

需要在某种形式，块或静态块的方法中。

public class GraphicalUserInterface {
    public static void main(String [] args) {  //  <=========

        String first_number = JOptionPane.showInputDialog("Enter first number");
        String second_number = JOptionPane.showInputDialog("Enter second number");

        int num1 = Integer.parseInt(first_number);
        int num2 = Integer.parseInt(second_number);
        int sum = num1 + num2;

        JOptionPane.showMessageDialog(null, "The answer is " +sum, "The Title", JOptionPane.INFORMATION_MESSAGE);

   } //  <=========
}

JOptionPane.showMessageDialog无效AnnotationName

1 个答案: