这是Thinking in java 2nd中的一个例子,希望对你有帮助。 //: c04:Garbage.java // Demonstration of the garbage // collector and finalizationclass Chair { static boolean gcrun = false; static boolean f = false; static int created = 0; static int finalized = 0; int i; Chair() { i = ++created; if(created == 47) System.out.println("Created 47"); } public void finalize() { if(!gcrun) { // The first time finalize() is called: gcrun = true; System.out.println( "Beginning to finalize after " + created + " Chairs have been created"); } if(i == 47) { System.out.println( "Finalizing Chair #47, " + "Setting flag to stop Chair creation"); f = true; } finalized++; if(finalized >= created) System.out.println( "All " + finalized + " finalized"); } }public class Garbage { public static void main(String[] args) { // As long as the flag hasn't been set, // make Chairs and Strings: while(!Chair.f) { new Chair(); new String("To take up space"); } System.out.println( "After all Chairs have been created:\n" + "total created = " + Chair.created + ", total finalized = " + Chair.finalized); // Optional arguments force garbage // collection & finalization: if(args.length > 0) { if(args[0].equals("gc") || args[0].equals("all")) { System.out.println("gc():"); System.gc(); } if(args[0].equals("finalize") || args[0].equals("all")) { System.out.println("runFinalization():"); System.runFinalization(); } } System.out.println("bye!"); } } ///:~
System.gc(),在你的main方法中进行,但是那个时候,aa还引用那块内存,所以不会被回收。如果你改成: public static void main(String[] args) { new A(); System.gc(); } 就会得到你想要的结果
Runs the garbage collector which deletes objects that are no longer in use.
也就是说,运行垃圾收集器把不再使用的对象删除。
当然輸出不是期望的"not checkin"
這個例子的用意也就是這樣呀
还有,既然是垃圾回收,就是不再有任何对象引用该类型分配
的内存地址,但是,你的A对象并没有释放
//: c04:Garbage.java
// Demonstration of the garbage
// collector and finalizationclass Chair {
static boolean gcrun = false;
static boolean f = false;
static int created = 0;
static int finalized = 0;
int i;
Chair() {
i = ++created;
if(created == 47)
System.out.println("Created 47");
}
public void finalize() {
if(!gcrun) {
// The first time finalize() is called:
gcrun = true;
System.out.println(
"Beginning to finalize after " +
created + " Chairs have been created");
}
if(i == 47) {
System.out.println(
"Finalizing Chair #47, " +
"Setting flag to stop Chair creation");
f = true;
}
finalized++;
if(finalized >= created)
System.out.println(
"All " + finalized + " finalized");
}
}public class Garbage {
public static void main(String[] args) {
// As long as the flag hasn't been set,
// make Chairs and Strings:
while(!Chair.f) {
new Chair();
new String("To take up space");
}
System.out.println(
"After all Chairs have been created:\n" +
"total created = " + Chair.created +
", total finalized = " + Chair.finalized);
// Optional arguments force garbage
// collection & finalization:
if(args.length > 0) {
if(args[0].equals("gc") ||
args[0].equals("all")) {
System.out.println("gc():");
System.gc();
}
if(args[0].equals("finalize") ||
args[0].equals("all")) {
System.out.println("runFinalization():");
System.runFinalization();
}
}
System.out.println("bye!");
}
} ///:~
public static void main(String[] args)
{
new A();
System.gc();
}
就会得到你想要的结果