Java中如何访问实例变量和方法

Question

这是一个用于访问实例变量和方法的 Java 程序（系统在全局声明“int puppyAge;”中预期的标记“int”导入上抛出语法错误：-

是否可以选择全局声明变量：

package instancevariableandmethods;
int puppyAge;

public class Instancevariable {
    public Instancevariable(String name) {
        System.out.println("The name is:" + name);
    }

    public void setAge(int age) {
        puppyAge = age;
    }

    public int getAge() {
        System.out.println("Puppy's age is: " + puppyAge);
        return puppyAge;
    }

    public static void main(String[] args) {
        Instancevariable myPuppy = new Instancevariable("tommy");

        /* Call class method to set puppy's age */
        myPuppy.setAge(2);

        /* Call another class method to get puppy's age */
        myPuppy.getAge();

        /* You can access instance variable as follows as well */
        System.out.println("Variable Value:" + myPuppy.puppyAge );
    }
}

Answer 1

像下面这样声明你的变量：

public class Instancevariable
{
    int puppyAge;
    //// The rest of your code
}

示例 - 全局和局部变量声明

public class Car {
    private int speed; // Private variable declaration
    public int wheels; // Public variable declaration

    /* ...constructor, etc... */

    public void speedUp() {
        // Local variable declaration, in line assignment,
        // only seen within the speedUp method
        int speedIncrease = 10;
        speed += speedIncrease;
    }
}

Answer 2

Java 中没有这样的全局变量。 类级别有静态变量，但它们在类的所有实例之间共享。

在这种情况下，您需要一个类字段：

package instancevariableandmethods;


public class Instancevariable
{
    int puppyAge;

    public Instancevariable(String name) {

        System.out.println("The name is: " + name);
    }


    public void setAge(int age) {

        puppyAge = age;
    }


    public int getAge() {

        System.out.println("Puppy's age is: " + puppyAge);
        return puppyAge;
    }

    public static void main(String[] args) {

        Instancevariable myPuppy = new Instancevariable("tommy");

        /* Call the class method to set the puppy's age */
        myPuppy.setAge(2);

        /* Call another class method to get the puppy's age */
        myPuppy.getAge();

        /* You can access instance variable as follows as well */
        System.out.println("Variable Value: " + myPuppy.puppyAge);
    }
}

Answer 3

你的int puppyAge; 属于类，不属于类：

public class Instancevariable {
    int puppyAge;
    // The rest of your code
}

Answer 4

你做错了。 你可以在你的类中声明一个类变量。 如果你想让它超级全球化，请使用“public”。

public class TemplateVO
{
    public int puppyAge;
    // The rest of your code