An Object Nothing Can Reach Any More

Four lines, and after the third one of the two objects created is already eligible for collection.

java

StringBuilder first = new StringBuilder("one");
StringBuilder second = new StringBuilder("two");

first = second;

System.out.println(first);

text

two

Line 4 pointed first at the second builder. Nothing else was holding the first one, so after that line there is no path from any root to it, and the collector may take it whenever it next looks.

What each variable reaches after line 4
After	`first` reaches	`second` reaches	Unreachable
Line 2	The `"one"` builder	The `"two"` builder	Nothing
Line 4	The `"two"` builder	The `"two"` builder	The `"one"` builder

Nothing was deleted, and no method was called to release anything. The object became garbage because the last reference moved, which is the only way anything ever becomes garbage.

Java
Garbage Collection