System.gc()为什么没有调用finalize()方法？

[cc945]

//下列程序为什么没有调用finalize()？
//改　Book novel=new Book(true)　为　new Book(true)　则调用finalize()，为什么？
//咨询finalize()和System.gc()使用经验！！

class Book {
boolean checkedOut=false ;

Book(boolean checkOut) {
checkedOut = checkOut;
}

void checkIn() {
checkedOut = false;
}

public void finalize() {
if(checkedOut)
System.out.println("Error: checked out");
}
}

public class TerminationCondition {
public static void main(String[] args) {
new Book(true);
System.gc();
}
}

[interhanchi]

^_^.这样改一下就可以了!
class Book {
boolean checkedOut=false ;

Book(boolean checkOut) {
checkedOut = checkOut;
}

void checkIn() {
checkedOut = false;
}

public void finalize() {
if(checkedOut)
System.out.println("Error: checked out");
}
}

public class TerminationCondition {
public static void main(String[] args) {
Book novel=new Book(true);
novel=null;
System.gc();
}
}