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comparison src/fschmidt/util/java/CollectionUtils.java @ 68:00520880ad02

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add fschmidt source
author Franklin Schmidt <fschmidt@gmail.com>
date Sun, 05 Oct 2025 17:24:15 -0600
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67:9d0fefce6985 68:00520880ad02
1 package fschmidt.util.java;
2
3 import java.util.Collection;
4 import java.util.Collections;
5 import java.util.Map;
6 import java.util.HashMap;
7 import java.util.List;
8 import java.util.ArrayList;
9 import java.util.Set;
10 import java.util.HashSet;
11 import java.util.LinkedHashSet;
12
13
14 public final class CollectionUtils {
15 private CollectionUtils() {} // never
16
17 public static <K,V> Map<K,V> optimizeMap(Map<K,V> map) {
18 switch( map.size() ) {
19 case 0:
20 return Collections.emptyMap();
21 case 1:
22 Map.Entry<K,V> entry = map.entrySet().iterator().next();
23 return Collections.singletonMap(entry.getKey(),entry.getValue());
24 default:
25 return new HashMap<K,V>(map);
26 }
27 }
28
29 public static <T> List<T> optimizeList(List<T> list) {
30 switch( list.size() ) {
31 case 0:
32 return Collections.emptyList();
33 case 1:
34 return Collections.singletonList(list.get(0));
35 default:
36 return new ArrayList<T>(list);
37 }
38 }
39
40 public static <T> Set<T> optimizeSet(Set<T> set) {
41 switch( set.size() ) {
42 case 0:
43 return Collections.emptySet();
44 case 1:
45 return Collections.singleton(set.iterator().next());
46 default:
47 return new HashSet<T>(set);
48 }
49 }
50
51 public static <T> Set<T> optimizeLinkedSet(Set<T> set) {
52 switch( set.size() ) {
53 case 0:
54 return Collections.emptySet();
55 case 1:
56 return Collections.singleton(set.iterator().next());
57 default:
58 return new LinkedHashSet<T>(set);
59 }
60 }
61
62 public static boolean intersects(Set set,Iterable col) {
63 for( Object obj : col ) {
64 if( set.contains(obj) )
65 return true;
66 }
67 return false;
68 }
69
70 public static boolean intersects(Set set,Object[] col) {
71 for( Object obj : col ) {
72 if( set.contains(obj) )
73 return true;
74 }
75 return false;
76 }
77
78 }