在 Java 中，我们可以从另一个类调用一个类的 main()方法吗？
原文:https://www . geesforgeks . org/in-Java-we-can-call-main-method-of-a-class-from-other-class/
在 Java 中，我们可以从另一个类调用一个类的 main()方法吗？ 或 如何从我们的代码中调用‘公共静态 void main(String[]args)’方法？
这些问题通常困扰着一个 Java 程序员。本文旨在以一种简单而有效的方式提供这些问题的答案。
正如我们所知，任何 Java 应用程序的 main()方法就像 Java 运行时环境首先调用 main()方法一样。所以很明显，我们不需要自己调用 main()方法，因为它已经在程序启动时被调用了。但是如果我们想从程序的某个地方调用 main()方法呢？这就是问题所在。
解决方案:
尽管 Java 不喜欢从程序中的其他地方调用 main()方法，但它也不禁止人们这样做。所以，事实上，我们可以随时随地调用 main()方法。
但是从我们的代码中调用 main()方法很棘手。会导致很多错误和异常，比如:
-
The main() method must be called from a static method only inside the same class.
```java // Java method to show that the main() method // must be called from a static method only // inside the same class
import java.io.*;
class GFG {
// The method that calls the main() method // Note that this method is not static void mainCaller() { System.out.println("mainCaller!");
// Calling the main() method main(null); }
// main() method public static void main(String[] args) { System.out.println("main");
// Calling the mainCalller() method // so that main() methiod is called externally mainCaller(); } } ```
Java 代码编译错误:
```java prog.java:27: error: non-static method mainCaller() cannot be referenced from a static context mainCaller(); ^ 1 error
```
-
The main() method must be passed the String[] args while calling it from somewhere else.
```java // Java method to show that the main() method // must be passed the String[] args // while calling it from somewhere else
import java.io.*;
class GFG {
// The method that calls the main() method static void mainCaller() { System.out.println("mainCaller!");
// Calling the main() method // Note that no parameter is passed main(); }
// main() method public static void main(String[] args) { System.out.println("main");
// Calling the mainCalller() method // so that main() methiod is called externally mainCaller(); } } ```
Java 代码编译错误:
```java prog.java:17: error: method main in class GFG cannot be applied to given types; main(); ^ required: String[] found: no arguments reason: actual and formal argument lists differ in length 1 error
```
-
Calling the main() method will lead to an infinite loop as the memory stack knows to run only the main() method.
```java // Java method to show that Calling the main() method // will lead to an infinite loop as the memory stack // knows to run only the main() method
import java.io.*;
class GFG {
// The method that calls the main() method static void mainCaller() { System.out.println("mainCaller!");
// Calling the main() method main(null); }
// main() method public static void main(String[] args) { System.out.println("main");
// Calling the mainCalller() method // so that main() methiod is called externally mainCaller(); } } ```
Java 代码中的运行时错误:
```java RunTime Error in java code :- Exception in thread "main" java.lang.StackOverflowError
mainCaller! main mainCaller! main mainCaller! main . . .
```
正确的做法:
示例 1: 从同一个类外部调用 main()方法
// Java method to show Calling main() method
// externally from the same class
import java.io.*;
class GFG {
static int count = 0;
// The method that calls the main() method
static void mainCaller()
{
System.out.println("mainCaller!");
count++;
// Calling the main() only 3 times
if (count < 3) {
// Calling the main() method
main(null);
}
}
// main() method
public static void main(String[] args)
{
System.out.println("main");
// Calling the mainCalller() method
// so that main() methiod is called externally
mainCaller();
}
}
输出:
main
mainCaller!
main
mainCaller!
main
mainCaller!
示例 1: 从另一个类外部调用 main()方法
// Java method to show Calling main() method
// externally from another class
import java.io.*;
class GFG {
static int count = 0;
// The method that calls the main() method
static void mainCaller()
{
System.out.println("mainCaller!");
count++;
// Calling the main() only 3 times
if (count < 3) {
// Calling the main() method
Test.main(null);
}
}
}
class Test {
// main() method
public static void main(String[] args)
{
System.out.println("main");
// Calling the mainCalller() method
// so that main() methiod is called externally
GFG.mainCaller();
}
}
输出:
main
mainCaller!
main
mainCaller!
main
mainCaller!
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