Java by API/java.lang.ref/SoftReference
new SoftReference(Object object, ReferenceQueue r)
<source lang="java">
import java.lang.ref.Reference; import java.lang.ref.ReferenceQueue; import java.lang.ref.SoftReference; import java.util.HashMap; public class Main {
public static void main(String[] args) { ReferenceQueue referenceQueue = new ReferenceQueue(); Object object = new Object() { public String toString() { return "Referenced Object"; } }; Object data = new Object() { public String toString() { return "Data"; } }; HashMap map = new HashMap(); Reference reference = new SoftReference(object, referenceQueue); map.put(reference, data); System.out.println(reference.get()); System.out.println(map.get(reference)); System.out.println(reference.isEnqueued()); System.gc(); System.out.println(reference.get()); System.out.println(map.get(reference)); System.out.println(reference.isEnqueued()); object = null; data = null; System.gc(); System.out.println(reference.get()); System.out.println(map.get(reference)); System.out.println(reference.isEnqueued()); }
}
</source>
new SoftReference(String referent)
<source lang="java">
import java.lang.ref.SoftReference; public class Main {
public static void main(String[] argv) throws Exception { SoftReference<String> sr = new SoftReference<String>("object"); Object o = sr.get(); if (o != null) { System.out.println(o); } else { System.out.println("collected or has been reclaimed"); } }
}
</source>
SoftReference: get()
<source lang="java">
import java.lang.ref.SoftReference; public class Main {
public static void main(String[] argv) throws Exception { SoftReference<String> sr = new SoftReference<String>("object"); Object o = sr.get(); if (o != null) { System.out.println(o); } else { System.out.println("collected or has been reclaimed"); } }
}
</source>