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sclass ValueOnDemandMap<A, B> extends AbstractMap<A, B> { Set<A> keys; // keys may be changed if map is changed IF1<A, B> makeValue; *() {} *(Set<A> *keys, IF1<A, B> *makeValue) {} // doesn't clone keys public B get(O a) { ret !containsKey(a) ? null : makeValue.get((A) a); } public bool containsKey(O a) { ret keys.contains(a); } public Set<Map.Entry<A, B>> entrySet() { ret new EntrySet; } final class EntrySet extends AbstractSet<Map.Entry<A,B>> { public final int size() { ret keys.size(); } public final void clear() { keys.clear(); } public final Iterator<Map.Entry<A,B>> iterator() { return mapI(keys.iterator(), key -> new Map.Entry<A, B>() { public A getKey() { ret key; } public B getValue() { ret makeValue.get(key); } public B setValue(B newValue) { throw unimplemented(); } }); } public final boolean contains(Object o) { if (o cast Map.Entry) ret keys.contains(o.getKey()); false; } public final boolean remove(Object o) { if (o cast Map.Entry) ret keys.remove(o.getKey()); false; } } public Set<A> keySet() { ret keys; } public int size() { ret keys.size(); } }
Began life as a copy of #1008575
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Snippet ID: | #1028138 |
Snippet name: | ValueOnDemandMap - map over a key set where values are calculated on every access |
Eternal ID of this version: | #1028138/12 |
Text MD5: | 95661ad9b4011faa89cd994cd2fdbca1 |
Transpilation MD5: | 1b44fe9d830feb8f1e170c857ecf974c |
Author: | stefan |
Category: | javax |
Type: | JavaX fragment (include) |
Public (visible to everyone): | Yes |
Archived (hidden from active list): | No |
Created/modified: | 2020-05-23 14:34:54 |
Source code size: | 1307 bytes / 47 lines |
Pitched / IR pitched: | No / No |
Views / Downloads: | 254 / 600 |
Version history: | 11 change(s) |
Referenced in: | [show references] |