java - 删除对象的引用

Question

我想删除测试器类中每个对象的引用，但出现错误。我使用的方法是在笔记中给我的，但不确定它们是否正确。

任何帮助将不胜感激:)

这是我的代码:

public class Bicycle {

// Instance Variables
private String name; // Owner's name
private int age; // Owner's age
private char gender; // Owner's gender
private static int instanceCounter = 0;

// Default Constructor - doesn't take in values
public Bicycle() {
    this("Not Given", 0, 'U');
    instanceCounter++;
}

// Parameter constructor
public Bicycle(String name, int age, char gender) {
    this.name = name;
    this.age = age;
    this.gender = gender;
    instanceCounter++;
}

// Getter and setters
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}

public int getAge() {
    return age;
}
public void setAge(int age) {
    this.age = age;
}

public char getGender() {
    return gender;
}
public void setGender(char gender) {
    this.gender = gender;
}

public int countInstances(){
    return instanceCounter;
}
}

测试人员:

public class BicycleTester {

  public static void main(String args[]){


    // Instance one
    Bicycle bicycle1 = new Bicycle(null, 0, 'U');
    bicycle1.setName("John");
    System.out.println("Name: " +bicycle1.getName());
    bicycle1.setAge(18);
    System.out.println("Age: " +bicycle1.getAge());
    bicycle1.setGender('M');
    System.out.println("Gender: " +bicycle1.getGender());

    System.out.println("");

    // Instance two
    Bicycle bicycle2 = new Bicycle(null, 0, 'U');
    bicycle2.setName("Mary");
    System.out.println("Name: " +bicycle2.getName());
    bicycle2.setAge(23);
    System.out.println("Age: " +bicycle2.getAge());
    bicycle2.setGender('F');
    System.out.println("Gender: " +bicycle2.getGender());

    System.out.println("");

    // Instance three
    Bicycle bicycle3 = new Bicycle(null, 0, 'U');
    bicycle3.setName("Billy");
    System.out.println("Name: " +bicycle3.getName());
    bicycle3.setAge(15);
    System.out.println("Age: " +bicycle3.getAge());
    bicycle3.setGender('M');
    System.out.println("Gender: " +bicycle3.getGender());

    System.out.println("");

    // Three ways to get rid of object's reference
    void go() {
        Life bicycle1 = new Life();
    }

    Life bicycle2 = new Life();
    bicycle2 = new Life();

    Life bicycle3 = new Life();
    bicycle3 = null;

}

}

Answer 1

好的，女士，让我们再回顾一下基础知识。

我们将从对象又名实例和引用之间的区别开始。

Life bike2 = new Life();

这里，bicycle2 是一个引用，它将位于堆栈上。该引用指向通过调用 new Life() 创建的实例。该实例将位于堆

上

您无法删除对象的引用。您可以删除实例。只有一种方法可以做到这一点。

1. 将指向实例的引用设置为null或指向其他实例示例:Life bike2 = new Life(); bicycle2 = null;//上面创建的实例将有资格进行GC

或者你也可以这样做:

Life bike2 = new Life();bicycle2 = new Life();//上面创建的life实例将被丢弃。

请注意:引用范围相关，一旦超出范围，它将无法访问。我认为您不是在这里谈论这个。