英文:
Why should a non static class method be used with instance?
问题
我现在正在学习关于静态和方法的知识，我对这些内容有一些疑问。
所以，我首先尝试了这个代码：
class Calculator{
int addNumbers(int a, int b){
return a + b;
}
}
public class Main {
public static void main(String[] args) {
System.out.println(Calculator.addNumbers(1, 23));
}
}
但我得到了以下错误信息：
Error:(11, 38) java: non-static method addNumbers(int,int) cannot be referenced from a static context
于是，我查找了一下，有人说我应该像下面这样在一个实例中调用方法，然后这个方法就能正常工作了：
class Calculator{
int addNumbers(int a, int b){
return a + b;
}
}
public class Main {
public static void main(String[] args) {
Calculator calculator = new Calculator();
System.out.println(calculator.addNumbers(1, 23));
}
}
我想知道为什么我不能在不使用实例的情况下使用非静态方法。
为什么类方法必须使用实例来调用？这只是规定吗？
到目前为止，我只是觉得由于 main() 方法是静态的，其他类中的所有内容都应该是静态的，才能在 main 方法中使用。
英文:
I'm studying about static and methods now.. and I have some questions about these..
So, I tried this one first
class Calculator{
int addNumbers(int a,int b){
return a+b;
}
}
public class Main {
public static void main(String[] args) {
System.out.println(Calculator.addNumbers(1,23));
}
}
And I got this error message
Error:(11, 38) java: non-static method addNumbers(int,int) cannot be referenced from a static context
So, I searched and people said I should call the method in an instance like below and it worked..
class Calculator{
int addNumbers(int a,int b){
return a+b;
}
}
public class Main {
public static void main(String[] args) {
Calculator calculator = new Calculator();
System.out.println(calculator.addNumbers(1,23));
}
}
I'm wondering why I can't use the non static method without using instance..
Why do class methods have to be used with instance? Is it just the rule??
So far I just feel like since main() method is static everything in other class should be static to be used in main method..
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