Java garbage collection -GC

Determining whether the object belongs to Garbage:

• Determining a reference number of objects
  • Determined by the number of reference objects is determined, whether the recovered, reference number = 0 is treated as waste
  • Each object instance, has a reference counter, referenced +1, -1 complete reference
  • Advantages: high efficiency, small impact of the implementation program
  • Cons: the case of circular references can not be detected, leading to memory leaks
• Reachability analysis algorithm
  • Determining whether the object referenced by the chain up, to determine whether the object can be recovered
  • GC Root objects can be used as follows:
    • 　　VM stack objects referenced (local variable table stack frame)
    • 　　The method of constant reference object region
    • 　　Method region static property class object reference
    • 　　Native method of native method stacks of reference objects
    •       Active thread object reference

Garbage collection algorithm:

1. Mark - sweep algorithm
   • Disadvantages: easily lead to fragmentation
2. Replication algorithm
   • For low survival rate of cases of Object
   • Solve the fragmentation problem
3. * Generational collection algorithm