为什么这个 Java 代码在 VS 代码中使用多个构造函数运行但不会用 javac 编译？

Question

我一直在尝试在 Java 中使用多个构造函数。下面是我的代码：

public class MultipleConstructors {
    int x = 20;
    int y = 50;
    String color = "Green";
    String color2 = "Yellow";

    public MultipleConstructors() {

    }

    public MultipleConstructors(int numb, int numb2, String colOne, String colTwo) {
        x = numb;
        y = numb2;
        color = colOne;
        color2 = colTwo;
    }

    public MultipleConstructors(int numb3, int numb4, String colThree, String colFour) {
        x = numb3;
        y = numb4; 
        color = colThree;
        color2 = colFour;
    }

    public MultipleConstructors(int numb5, int numb6, String colFive, String colSix) {
        x = numb5;
        y = numb6; 
        color = colFive;
        color2 = colSix;
    }

    public static void main(String[] args) {
        MultipleConstructors myObjOne = new MultipleConstructors(100, 200, "Pink", "Blue");
        MultipleConstructors myObjTwo = new MultipleConstructors(300, 500, "Burgandy", "Silver");
        MultipleConstructors myObjThree = new MultipleConstructors(800, 1000, "Black", "White");
        MultipleConstructors myObjFour = new MultipleConstructors();

        System.out.println(myObjOne.x + myObjOne.y + " " + myObjOne.color + " " + myObjTwo.color2 + " " + " : SUCCESS");

        System.out.println(myObjTwo.x + myObjTwo.y + " " + myObjTwo.color + " " + myObjTwo.color2 + " " + " : VICTORY");

        System.out.println(myObjThree.x + myObjThree.y + " " + myObjThree.color + " " + myObjThree.color2 + " " + " : YES");

        System.out.println(myObjFour.x + myObjFour.y + " " + myObjFour.color + " " + myObjFour.color2 + " " + " : YES");
    }
}

它在 VS Code 中运行，但不会使用 javac 命令编译。我认为它可能是父属性声明之后未定义的构造函数public MultipleConstructors() {}。

Answer 1

如果您收到类似于以下错误消息的内容：

MultipleConstructors.java:11: error: constructor MultipleConstructors(int,int,java.lang.String,java.lang.String) is already defined in class MultipleConstructors

那么你应该使用这个答案。如果您有 ClassNotFoundException，您应该看到 Ntshembo Hlongwane 的回答。

你的问题是你有多个相同的构造函数。我认为你想要的是构造函数重载，这意味着你可以有多个具有不同 header 的构造函数，但是你的三个构造函数具有相同的 header。请在下面查看我与您的构造函数内联的评论：

public MultipleConstructors() {
    // header has no parameters
    // fine, leaves values alone
}

public MultipleConstructors(int numb, int numb2, String colOne, String colTwo) {
    // header has parameters int, int String String
    //fine, offers you the opportunity to change those values

    x = numb;
    y = numb2;
    color = colOne;
    color2 = colTwo;
}

public MultipleConstructors(int numb3, int numb4, String colThree, String colFour) {
    // header has parameters int, int, String, String
    // Wait, that's the same as the one above!

    x = numb3;
    y = numb4; 
    color = colThree;
    color2 = colFour;
}

public MultipleConstructors(int numb5, int numb6, String colFive, String colSix) {
    // header has parameters int, int, String, String
    // Wait, that's also the same as the one above!

    x = numb5;
    y = numb6; 
    color = colFive;
    color2 = colSix;
}

当您实例化这个 object 并给它两个整数和一个字符串时，您希望调用哪个构造函数？这是逻辑错误，不是语法错误或编译器错误，因为你的代码有歧义。希望这对您有所帮助，并祝您在学习过程中好运。 :)

Answer 2

基于运行ning代码时发现的异常

Correct, runs in VSCode but won't compile in order to run in terminal. It throws the error "could not find or load main class " caused by "ClassNotFoundException"

这是由于：

假设您将文件命名为 Test.java
然后在您的代码中将 class 写为 MyTest
当您尝试运行代码 java Test 时，您会收到以下错误：

Error: Could not find or load main class Test
Caused by: java.lang.ClassNotFoundException: Test

这是因为 Java 现在创建了一个 MyTest.class，您必须运行而不是

为什么这个 Java 代码在 VS 代码中使用多个构造函数运行但不会用 javac 编译？

Why does this Java code using multiple constructors run in VS code but won't compile with javac?

java

visual-studio-code

constructor

javac

为什么这个 Java 代码在 VS 代码中使用多个构造函数 运行 但不会用 javac 编译？

Why does this Java code using multiple constructors run in VS code but won't compile with javac?

java

visual-studio-code

constructor

javac

为什么这个 Java 代码在 VS 代码中使用多个构造函数运行但不会用 javac 编译？