Java新手编写加法私有函数遇报错：变量未解析等问题求助

核心错误点 #

• 代码执行逻辑位置错误：Java类中，变量赋值、方法调用这类执行语句不能直接写在类的根层级，必须放在方法（比如main方法）内部。
• 变量未声明类型：outputMessageString未声明数据类型，Java是强类型语言，所有变量必须先明确类型才能使用。
• 静态与非静态成员冲突：addTwoNumbersAndReturnAdditionResult是静态方法，直接访问类的非静态成员变量（number1Integer、number2Integer等）会触发编译错误，要么把成员变量改为静态，要么通过实例化对象调用非静态方法。

修正后的代码（静态成员方案） #

import javax.swing.*;

public class Note12FunctionExamples {
    // 改为静态变量，适配静态方法调用
    static int number1Integer = 0;
    static int number2Integer = 0;
    static int additionResultInteger = 0;

    public static void main(String[] args) {
        number1Integer = 3;
        number2Integer = 4;
        
        additionResultInteger = addTwoNumbersAndReturnAdditionResult(number1Integer, number2Integer);
        // 声明String类型变量
        String outputMessageString = number1Integer + " + " + number2Integer + " is: " + additionResultInteger;
        JOptionPane.showMessageDialog(null, outputMessageString);
    }

    private static int addTwoNumbersAndReturnAdditionResult(int number1Integer, int number2Integer) {
        int additionResultInteger = 0;
        additionResultInteger = number1Integer + number2Integer;
        return additionResultInteger;
    }
}

可选修正方案（实例化对象方案） #

如果不想将成员变量改为静态，可以通过实例化类对象来调用非静态方法：

import javax.swing.*;

public class Note12FunctionExamples {
    int number1Integer = 0;
    int number2Integer = 0;
    int additionResultInteger = 0;

    public static void main(String[] args) {
        Note12FunctionExamples instance = new Note12FunctionExamples();
        instance.number1Integer = 3;
        instance.number2Integer = 4;
        
        instance.additionResultInteger = instance.addTwoNumbersAndReturnAdditionResult(instance.number1Integer, instance.number2Integer);
        String outputMessageString = instance.number1Integer + " + " + instance.number2Integer + " is: " + instance.additionResultInteger;
        JOptionPane.showMessageDialog(null, outputMessageString);
    }

    // 去掉static修饰符，改为非静态方法
    private int addTwoNumbersAndReturnAdditionResult(int number1Integer, int number2Integer) {
        int additionResultInteger = 0;
        additionResultInteger = number1Integer + number2Integer;
        return additionResultInteger;
    }
}

内容的提问来源于stack exchange，提问作者jack pipkins