Java GC系列（2）：Java垃圾回收是如何工作的？

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class Animal {

    public static void main(String[] args) {

        Animal lion = new Animal();

        System.out.println("Main is completed.");

    }

    protected void finalize() {

        System.out.println("Rest in Peace!");

    }

}

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Class GCScope {

    GCScope t;

    static int i = 1;

    public static void main(String args[]) {

        GCScope t1 = new GCScope();

        GCScope t2 = new GCScope();

        GCScope t3 = new GCScope();

        // No Object Is Eligible for GC

        t1.t = t2; // No Object Is Eligible for GC

        t2.t = t3; // No Object Is Eligible for GC

        t3.t = t1; // No Object Is Eligible for GC

        t1 = null;

        // No Object Is Eligible for GC (t3.t still has a reference to t1)

        t2 = null;

        // No Object Is Eligible for GC (t3.t.t still has a reference to t2)

        t3 = null;

        // All the 3 Object Is Eligible for GC (None of them have a reference.

        // only the variable t of the objects are referring each other in a

        // rounded fashion forming the Island of objects with out any external

        // reference)

    }

    protected void finalize() {

        System.out.println("Garbage collected from object" + i);

        i++;

    }

class GCScope {

    GCScope t;

    static int i = 1;

    public static void main(String args[]) {

        GCScope t1 = new GCScope();

        GCScope t2 = new GCScope();

        GCScope t3 = new GCScope();

        // 没有对象符合GC

        t1.t = t2; // 没有对象符合GC

        t2.t = t3; // 没有对象符合GC

        t3.t = t1; // 没有对象符合GC

        t1 = null;

        // 没有对象符合GC (t3.t 仍然有一个到 t1 的引用)

        t2 = null;

        // 没有对象符合GC (t3.t.t 仍然有一个到 t2 的引用)

        t3 = null;

        // 所有三个对象都符合GC (它们中没有一个拥有引用。

        // 只有各对象的变量 t 还指向了彼此，

        // 形成了一个由对象组成的环形的岛，而没有任何外部的引用。)

    }

    protected void finalize() {

        System.out.println("Garbage collected from object" + i);

        i++;

    }

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import java.util.LinkedList;

import java.util.List;

public class GC {

    public static void main(String[] main) {

        List l = new LinkedList();

        // Enter infinite loop which will add a String to the list: l on each

        // iteration.

        do {

            l.add(new String("Hello, World"));

        } while (true);

    }

}

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Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

    at java.util.LinkedList.linkLast(LinkedList.java:142)

    at java.util.LinkedList.add(LinkedList.java:338)

    at com.javapapers.java.GCScope.main(GCScope.java:12)