java中的字符串文字和垃圾收集器

问题描述

更具体地说，我已经读过，在java 7中，字符串文字现在存储在堆的主要部分，所以它们是否有资格使用垃圾回收器？

 字符串a =z; 
 a = null; 
  

现在对象z被垃圾收集，或者仍然在字符串池中作为匿名对象？

解决方案

只有当所有包含这些文字的类都是GCed时，字符串文字才能被GCed，而这只会在ClassLoaders加载这些类是GCed。

示例：

  public interface I { 
 String getString（）; 
} 
 
 public class Test2 implements I {
 String s =X; 
 @Override 
 public String getString（）{
 return s; 
} 
} 
 
 public class Test implements I {
 String s =X; 
 @Override 
 public String getString（）{
 return s; 
 
 
 
 public class Test1 {
 
 public static void main（String [] args）throws Exception {
 ClassLoader cl = new URLClassLoader（new URL [] {new URL（file：d：/ test /）}）; 
 I i =（I）cl.loadClass（Test）。newInstance（）; 
 WeakReference w = new WeakReference（i.getString（））; //向文字X的微弱引用
 i = null; 
 cl = null; 
 System.out.println（w.get（））; 
 System.gc（）; 
 Thread.sleep（1000）; 
 System.out.println（w.get（））; 
 
 
 
 
 
 
 $ b 
编译这些类，将Test.class移动到d： / test，以便系统类加载器不能看到它，然后运行main。你会看到
  X 
 null 
  
这意味着X是GC ed  
To be more specific I've read that in java 7 string literal are now stored in the main part of the heap so, do they become eligible for garbage collector?
String a ="z";
a = null;
Now does the object "z" get garbage collected,or still in the string pool as an anonymous object ?
 解决方案 
String literals can only be GCed when all classes contaning these literals are GCed which in turn can only happen if ClassLoaders which loaded these classes are GCed.
Example:
public interface I {
    String getString();
}

public class Test2 implements I {
    String s = "X";
    @Override
    public String getString() {
        return s;
    }
}

public class Test implements I {
    String s = "X";
    @Override
    public String getString() {
        return s;
    }
}

public class Test1 {

    public static void main(String[] args) throws Exception {
        ClassLoader cl = new URLClassLoader(new URL[] {new URL("file:d:/test/")});
        I i = (I)cl.loadClass("Test").newInstance();
        WeakReference w = new WeakReference(i.getString()); //weak ref to "X" literal
        i = null;
        cl = null;
        System.out.println(w.get());
        System.gc();
        Thread.sleep(1000);
        System.out.println(w.get());
    }
}
compile these classes, move Test.class to d:/test so that system class loader cannot see it, then run main. You will see
X
null
which means "X" was GC ed
                        
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