java - 找不到符号且函数无法应用: Java

Question

class Demo2 
{
    int i=1,j=2;
    void fun1()
    {
        i=i+1;
        j=j+1;
    }
    public static void main(String[] args) 
    {

        Demo2 d1=new Demo2();
        d1.fun1();
        d1.fun1();
        d1.fun1();
        System.out.println("Hello World!");
    }
}

符号无法找到并且功能无法应用错误显示请帮助我，我是一个基础学习者......

Answer 1

代码中有几个错误。我评论并建议了一些工作代码。

class Demo2 
{

    void fun1()
    {
        i=i+1; //i has not been initialized
        j=j+1; //j has not been initialized 
    }
    public static void main(String[] args) 
    {

        Demo2 d1=new Demo2();
        d1.fun1(1);//"fun1" does not accept a parameter.
        d1.fun1();
        d1.fun1();
        System.out.println("Hello World!");
    }
}

这里是一个可以运行的 Demo2 类，可以帮助您:

class Demo2
{
    int i = 0;
    int j = 0;

    public void fun1(int param)
    {
        i=i+param;
        j=j+param;
    }

    public static void main(String[] args)
    {
        Demo2 d = new Demo2();
        d.fun1(1);//adds 1 to both i and j
        d.fun1(2);//adds 2 to both i and j
        System.out.println("i is equal to " + i);
        System.out.println("j is equal to " + j);  
    }
}