Java - 如何访问在 void 函数中创建的数组

Question

感谢那些帮助我走到这一步的人。我做了一些改变。现在，在方法 Method() 中分配 array1 的行上出现错误。 (编辑后的版本如下所示)

公共(public)类JavaApplication2 {

int[] array1;
public JavaApplication2()
{
}

public static void main(String[] args) {
    JavaApplication2 obj = new JavaApplication2();
    obj.method();
    System.out.print(obj.array1[1]);
}

public void method()
{
    array1 = {1,1,1,1,1,1};
}

}

Answer 1

它们是在同一个类中定义的；然而它们是在方法内声明的，因此它们是局部变量。这意味着它们仅存在于各自的方法中，特别是仅存在于该方法的单次调用。本质上，它们会在方法退出时消失，并在每次调用该方法时重新创建。

引用the tutorial :

• Local Variables Similar to how an object stores its state in fields, a method will often store its temporary state in local variables. The syntax for declaring a local variable is similar to declaring a field (for example, int count = 0;). There is no special keyword designating a variable as local; that determination comes entirely from the location in which the variable is declared — which is between the opening and closing braces of a method. As such, local variables are only visible to the methods in which they are declared; they are not accessible from the rest of the class.

您可能意味着它们是字段(也称为实例变量)，这意味着类的每个实例化对象都有自己的“个人”变量，该变量与“拥有”它的对象一起持续存在。字段在类内部但在方法外部声明。

public class JavaApplication2 {
    int[] array1; // variable declaration
                  // begins with the type of the variable

    public JavaApplication2() {}

    public void method() {
        array1 = {1,1,1,1,1,1}; // assignment
    }                           // begins with an identifier
}

通常，字段在构造函数期间初始化一次，因此您不必调用单独的方法来执行此操作。

public class JavaApplication2 {
    int[] array1;

    public JavaApplication2() {
        array1 = {1,1,1,1,1,1};
    }
}