Java Virtual Machine (v) four types of reference levels for Java

1. Preface

Hotspot has adopted a accessibility analysis algorithm to determine whether an object can be used by a GC, whether it is a reference or an accessibility analysis algorithm to determine whether an object exists or not. If the value stored in the data of type reference represents the starting address of another piece of memory, it is said that this memory represents a reference. To enrich the description of the relationship between objects and objects, in order to implement the system cache, Java has established four types of reference levels.

2. Four levels of reference

After JDK1.2, Java extends the concept of references into strong, soft, weak, and virtual references in 4 ways, 4 of which are weakened in turn.

Finally, the following diagram is used to understand how the JVM recycling mechanism treats the various reference types differently:

Java Virtual Machine (v) four types of reference levels for Java