java 不能从 **静态上下文** 引用非静态方法。这里的静态内容是什么？
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non-static method cannot be referenced from a **static context**. What is static content here?
提问by Jeffery
I am writing a program to get input from a text file (only contain integers), put it into linked list and display the linked list. Here is my code:
我正在编写一个程序来从文本文件（仅包含整数）中获取输入，将其放入链表并显示链表。这是我的代码：
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
class Node{
int value;
Node next;
Node(){
next = null;
}
}
public class ReverseLL{
public static void main(String[] args) throws FileNotFoundException{
Scanner in = new Scanner(new File("input.txt"));
Node head = null;
Node tail = null;
while(in.hasNextInt()){
Node ptr = new Node();
ptr.value = in.nextInt();
if(head == null){
head = ptr;
tail = ptr;
}else{
tail.next = ptr;
}
tail = ptr;
}
display(head);
in.close();
}
static void display(Node head){
while(head!=null){
System.out.print(head.value + " " + "\n");
head = head.next;
}
}
}
It works now after I changed the display method to be static. However before I changed to static. The error said non-static method display(Node) cannot be referenced from a **static contextI read some document about the static and no-static. To call a no-static, I need to instantiate an instance then call like instance.method. To call static method, you can call like "class.method". My question is based on my program. I did not create the method in other class, why I need to change to static method? What is the so called static content? Thank you for explaining it to me.
在我将显示方法更改为static后，它现在可以工作了。但是在我改成静态之前。错误说不能从 **static 上下文中引用非静态方法 display(Node)我阅读了一些关于静态和非静态的文档。要调用非静态，我需要实例化一个实例，然后像 instance.method 一样调用。要调用静态方法，您可以像“class.method”一样调用。我的问题是基于我的程序。我没有在其他类中创建方法，为什么要改为静态方法？什么是所谓的静态内容？谢谢你给我解释。
回答by Jon Are Wisting
Your main-method is the static context, and you are trying to call the non-static method display() from it. That doesn't work even if it is in the same class. To have the disply method non-static you have to do this.
您的主要方法是静态上下文，您正在尝试从中调用非静态方法 display()。即使在同一个班级，那也行不通。要使显示方法非静态，您必须这样做。
public static void main(String[] args) throws FileNotFoundException{
ReverseLL r = new ReverseLL();
r.display(head);
}
public void display(Node head){
...
}
回答by Shree Naath
static context of calling :
调用的静态上下文：
Class_Name.method_name();
non-static context of calling :
调用的非静态上下文：
Class_Name object_name = new Class_Name();
object_name.method_name();
You should not call a non static method using a static context and vice versa.
您不应使用静态上下文调用非静态方法，反之亦然。
回答by Tadija Bagari?
You are calling your displaymethod from the public static void main(String[] args)method.
您正在display从public static void main(String[] args)方法中调用您的方法。
To work around having to static methods you could do:
要解决必须使用静态方法的问题，您可以执行以下操作：
public class ReverseLL{
public void run() throws FileNotFoundException{
Scanner in = new Scanner(new File("input.txt"));
Node head = null;
Node tail = null;
while(in.hasNextInt()){
Node ptr = new Node();
ptr.value = in.nextInt();
if(head == null){
head = ptr;
tail = ptr;
}else{
tail.next = ptr;
}
tail = ptr;
}
display(head);
in.close();
}
void display(Node head){
while(head!=null){
System.out.print(head.value + " " + "\n");
head = head.next;
}
}
public static void main(String[] args){
ReverseLL reverseLL = new ReverseLL();
try{
reverseLL.run();
}catch(FileNotFoundException e){
// handle ex...
}
}
}
回答by Yasir
you can also use the new ReverseLL().dislpay(head);it will root out the problem .
你也可以使用新的 ReverseLL().dislpay(head);它会根除问题。
回答by GoatyGuy
Simply said, "static" methods exist on class level, while "non-static" methods exist on instance level. You don′t have an instance of your class in your psvm-method, from where you could call the non-static method. So this method simply doesn′t exist.
简单地说，“静态”方法存在于类级别，而“非静态”方法存在于实例级别。您的 psvm-method 中没有您的类的实例，您可以从中调用非静态方法。所以这种方法根本不存在。
You can read more from this post: What is the reason behind "non-static method cannot be referenced from a static context"?
您可以从这篇文章中阅读更多内容： “不能从静态上下文中引用非静态方法”背后的原因是什么？
