2019101701(课后作业部分)

代码如下，其中finalize方法为考虑到对象万一被垃圾回收时减少一次计数：

public class Example {
    private static int classCounter = 0;

    public Example() {
        classCounter = classCounter + 1;
    }

    public void finalize() {
        classCounter = classCounter - 1;
    }

    public static int getClassCount() {
        return classCounter;
    }

    public static void main(String[] args) {
        Example exp = new Example();
        System.out.println(Example.getClassCount());
        Example exp1 = new Example();
        Example exp2 = new Example();
        System.out.println(Example.getClassCount());
    }
}