Package net.cscott.jutil

Interface Environment<K,V>

All Superinterfaces:

Map<K,V>

All Known Implementing Classes:

HashEnvironment, PersistentEnvironment

public interface Environment<K,V>
extends Map<K,V>

An Environment is a Map with scoping: you can save marks into the environment and undo all changes since a mark.

Closing a mark undoes all changes since the mark, so a try-with-resources statement makes a scope:

 try (Environment.Mark scope = env.getMark()) {
     env.put("x", 1); // the binding of x until the end of the block
     ...
 } // x has its old binding, or none, again
 

(javac -Xlint:try warns that scope is not used in the block; Java 22 and later can name it _ instead.)

Author:

C. Scott Ananian <cananian@alumni.princeton.edu>

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	Environment.Mark	A mark into an environment.

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Method Summary

Modifier and Type	Method	Description
Environment.Mark	getMark()	Get a mark that will allow you to restore the current state of this environment.
void	undoToMark(Environment.Mark m)	Undo all changes since the supplied mark, restoring the map to its state at the time the mark was taken.

Methods inherited from interface java.util.Map

clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keySet, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values

Method Details

getMark

Environment.Mark getMark()

Get a mark that will allow you to restore the current state of this environment.

undoToMark

void undoToMark(Environment.Mark m)

Undo all changes since the supplied mark, restoring the map to its state at the time the mark was taken. The undoToMark() operation must be repeatable.

Throws:

IllegalArgumentException - if the mark is not one of this environment's (in HashEnvironment and PersistentEnvironment; since 2.0)