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431 lines
12 KiB
Markdown
431 lines
12 KiB
Markdown
[TOC]
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<!-- Appendix: Collection Topics -->
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# 附录:集合主题
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> 本附录是一些比[第十二章 集合]()中介绍的更高级的内容。
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<!-- Sample Data -->
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## 示例数据
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这里创建一些样本数据用于集合示例。 以下数据将颜色名称与HTML颜色的RGB值相关联。请注意，每个键和值都是唯一的：
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```java
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// onjava/HTMLColors.java
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// Sample data for collection examples
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package onjava;
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import java.util.*;
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import java.util.stream.*;
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import java.util.concurrent.*;
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public class HTMLColors {
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public static final Object[][] ARRAY = {
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{ 0xF0F8FF, "AliceBlue" },
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{ 0xFAEBD7, "AntiqueWhite" },
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{ 0x7FFFD4, "Aquamarine" },
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{ 0xF0FFFF, "Azure" },
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{ 0xF5F5DC, "Beige" },
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{ 0xFFE4C4, "Bisque" },
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{ 0x000000, "Black" },
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{ 0xFFEBCD, "BlanchedAlmond" },
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{ 0x0000FF, "Blue" },
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{ 0x8A2BE2, "BlueViolet" },
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{ 0xA52A2A, "Brown" },
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{ 0xDEB887, "BurlyWood" },
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{ 0x5F9EA0, "CadetBlue" },
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{ 0x7FFF00, "Chartreuse" },
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{ 0xD2691E, "Chocolate" },
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{ 0xFF7F50, "Coral" },
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{ 0x6495ED, "CornflowerBlue" },
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{ 0xFFF8DC, "Cornsilk" },
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{ 0xDC143C, "Crimson" },
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{ 0x00FFFF, "Cyan" },
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{ 0x00008B, "DarkBlue" },
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{ 0x008B8B, "DarkCyan" },
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{ 0xB8860B, "DarkGoldenRod" },
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{ 0xA9A9A9, "DarkGray" },
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{ 0x006400, "DarkGreen" },
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{ 0xBDB76B, "DarkKhaki" },
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{ 0x8B008B, "DarkMagenta" },
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{ 0x556B2F, "DarkOliveGreen" },
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{ 0xFF8C00, "DarkOrange" },
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{ 0x9932CC, "DarkOrchid" },
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{ 0x8B0000, "DarkRed" },
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{ 0xE9967A, "DarkSalmon" },
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{ 0x8FBC8F, "DarkSeaGreen" },
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{ 0x483D8B, "DarkSlateBlue" },
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{ 0x2F4F4F, "DarkSlateGray" },
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{ 0x00CED1, "DarkTurquoise" },
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{ 0x9400D3, "DarkViolet" },
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{ 0xFF1493, "DeepPink" },
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{ 0x00BFFF, "DeepSkyBlue" },
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{ 0x696969, "DimGray" },
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{ 0x1E90FF, "DodgerBlue" },
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{ 0xB22222, "FireBrick" },
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{ 0xFFFAF0, "FloralWhite" },
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{ 0x228B22, "ForestGreen" },
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{ 0xDCDCDC, "Gainsboro" },
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{ 0xF8F8FF, "GhostWhite" },
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{ 0xFFD700, "Gold" },
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{ 0xDAA520, "GoldenRod" },
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{ 0x808080, "Gray" },
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{ 0x008000, "Green" },
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{ 0xADFF2F, "GreenYellow" },
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{ 0xF0FFF0, "HoneyDew" },
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{ 0xFF69B4, "HotPink" },
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{ 0xCD5C5C, "IndianRed" },
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{ 0x4B0082, "Indigo" },
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{ 0xFFFFF0, "Ivory" },
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{ 0xF0E68C, "Khaki" },
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{ 0xE6E6FA, "Lavender" },
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{ 0xFFF0F5, "LavenderBlush" },
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{ 0x7CFC00, "LawnGreen" },
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{ 0xFFFACD, "LemonChiffon" },
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{ 0xADD8E6, "LightBlue" },
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{ 0xF08080, "LightCoral" },
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{ 0xE0FFFF, "LightCyan" },
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{ 0xFAFAD2, "LightGoldenRodYellow" },
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{ 0xD3D3D3, "LightGray" },
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{ 0x90EE90, "LightGreen" },
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{ 0xFFB6C1, "LightPink" },
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{ 0xFFA07A, "LightSalmon" },
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{ 0x20B2AA, "LightSeaGreen" },
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{ 0x87CEFA, "LightSkyBlue" },
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{ 0x778899, "LightSlateGray" },
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{ 0xB0C4DE, "LightSteelBlue" },
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{ 0xFFFFE0, "LightYellow" },
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{ 0x00FF00, "Lime" },
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{ 0x32CD32, "LimeGreen" },
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{ 0xFAF0E6, "Linen" },
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{ 0xFF00FF, "Magenta" },
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{ 0x800000, "Maroon" },
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{ 0x66CDAA, "MediumAquaMarine" },
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{ 0x0000CD, "MediumBlue" },
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{ 0xBA55D3, "MediumOrchid" },
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{ 0x9370DB, "MediumPurple" },
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{ 0x3CB371, "MediumSeaGreen" },
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{ 0x7B68EE, "MediumSlateBlue" },
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{ 0x00FA9A, "MediumSpringGreen" },
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{ 0x48D1CC, "MediumTurquoise" },
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{ 0xC71585, "MediumVioletRed" },
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{ 0x191970, "MidnightBlue" },
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{ 0xF5FFFA, "MintCream" },
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{ 0xFFE4E1, "MistyRose" },
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{ 0xFFE4B5, "Moccasin" },
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{ 0xFFDEAD, "NavajoWhite" },
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{ 0x000080, "Navy" },
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{ 0xFDF5E6, "OldLace" },
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{ 0x808000, "Olive" },
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{ 0x6B8E23, "OliveDrab" },
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{ 0xFFA500, "Orange" },
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{ 0xFF4500, "OrangeRed" },
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{ 0xDA70D6, "Orchid" },
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{ 0xEEE8AA, "PaleGoldenRod" },
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{ 0x98FB98, "PaleGreen" },
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{ 0xAFEEEE, "PaleTurquoise" },
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{ 0xDB7093, "PaleVioletRed" },
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{ 0xFFEFD5, "PapayaWhip" },
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{ 0xFFDAB9, "PeachPuff" },
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{ 0xCD853F, "Peru" },
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{ 0xFFC0CB, "Pink" },
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{ 0xDDA0DD, "Plum" },
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{ 0xB0E0E6, "PowderBlue" },
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{ 0x800080, "Purple" },
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{ 0xFF0000, "Red" },
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{ 0xBC8F8F, "RosyBrown" },
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{ 0x4169E1, "RoyalBlue" },
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{ 0x8B4513, "SaddleBrown" },
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{ 0xFA8072, "Salmon" },
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{ 0xF4A460, "SandyBrown" },
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{ 0x2E8B57, "SeaGreen" },
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{ 0xFFF5EE, "SeaShell" },
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{ 0xA0522D, "Sienna" },
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{ 0xC0C0C0, "Silver" },
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{ 0x87CEEB, "SkyBlue" },
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{ 0x6A5ACD, "SlateBlue" },
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{ 0x708090, "SlateGray" },
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{ 0xFFFAFA, "Snow" },
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{ 0x00FF7F, "SpringGreen" },
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{ 0x4682B4, "SteelBlue" },
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{ 0xD2B48C, "Tan" },
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{ 0x008080, "Teal" },
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{ 0xD8BFD8, "Thistle" },
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{ 0xFF6347, "Tomato" },
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{ 0x40E0D0, "Turquoise" },
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{ 0xEE82EE, "Violet" },
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{ 0xF5DEB3, "Wheat" },
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{ 0xFFFFFF, "White" },
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{ 0xF5F5F5, "WhiteSmoke" },
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{ 0xFFFF00, "Yellow" },
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{ 0x9ACD32, "YellowGreen" },
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};
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public static final Map<Integer,String> MAP =
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Arrays.stream(ARRAY)
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.collect(Collectors.toMap(
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element -> (Integer)element[0],
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element -> (String)element[1],
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(v1, v2) -> { // Merge function
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throw new IllegalStateException();
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},
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LinkedHashMap::new
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));
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// Inversion only works if values are unique:
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public static <V, K> Map<V, K>
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invert(Map<K, V> map) {
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return map.entrySet().stream()
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.collect(Collectors.toMap(
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Map.Entry::getValue,
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Map.Entry::getKey,
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(v1, v2) -> {
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throw new IllegalStateException();
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},
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LinkedHashMap::new
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));
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}
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public static final Map<String,Integer>
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INVMAP = invert(MAP);
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// Look up RGB value given a name:
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public static Integer rgb(String colorName) {
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return INVMAP.get(colorName);
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}
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public static final List<String> LIST =
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Arrays.stream(ARRAY)
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.map(item -> (String)item[1])
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.collect(Collectors.toList());
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public static final List<Integer> RGBLIST =
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Arrays.stream(ARRAY)
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.map(item -> (Integer)item[0])
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.collect(Collectors.toList());
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public static
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void show(Map.Entry<Integer,String> e) {
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System.out.format(
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"0x%06X: %s%n", e.getKey(), e.getValue());
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}
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public static void
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show(Map<Integer,String> m, int count) {
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m.entrySet().stream()
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.limit(count)
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.forEach(e -> show(e));
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}
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public static void show(Map<Integer,String> m) {
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show(m, m.size());
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}
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public static
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void show(Collection<String> lst, int count) {
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lst.stream()
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.limit(count)
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.forEach(System.out::println);
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}
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public static void show(Collection<String> lst) {
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show(lst, lst.size());
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}
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public static
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void showrgb(Collection<Integer> lst, int count) {
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lst.stream()
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.limit(count)
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.forEach(n -> System.out.format("0x%06X%n", n));
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}
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public static void showrgb(Collection<Integer> lst) {
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showrgb(lst, lst.size());
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}
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public static
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void showInv(Map<String,Integer> m, int count) {
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m.entrySet().stream()
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.limit(count)
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.forEach(e ->
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System.out.format(
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"%-20s 0x%06X%n", e.getKey(), e.getValue()));
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}
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public static void showInv(Map<String,Integer> m) {
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showInv(m, m.size());
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}
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public static void border() {
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System.out.println(
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"******************************");
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}
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}
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```
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**MAP** 是使用Streams（[第十四章 流式编程]()）创建的。 二维数组 **ARRAY** 作为流传输到 **Map** 中，但请注意我们不仅仅是使用简单版本的 **Collectors.toMap()** 。 那个版本生成一个 **HashMap** ，它使用散列函数来控制对键的排序。 为了保留原来的顺序，我们必须将键值对直接放入 **TreeMap** 中，这意味着我们需要使用更复杂的 **Collectors.toMap()** 版本。这需要两个函数从每个流元素中提取键和值，就像简单版本的**Collectors.toMap()** 一样。 然后它需要一个*合并函数*（merge function），它解决了与同一个键相关的两个值之间的冲突。这里的数据已经预先审查过，因此绝不会发生这种情况，如果有的话，这里会抛出异常。最后，传递生成所需类型的空map的函数，然后用流来填充它。
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**rgb()** 方法是一个便捷函数（convenience function），它接受颜色名称 **String** 参数并生成其数字RGB值。为此，我们需要一个反转版本的 **COLORS** ，它接受一个 **String**键并查找RGB的 **Integer** 值。 这是通过 **invert()** 方法实现的，如果任何 **COLORS** 值不唯一，则抛出异常。
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我们还创建包含所有名称的 **LIST** ，以及包含十六进制表示法的RGB值的 **RGBLIST** 。
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第一个 **show()** 方法接受一个 **Map.Entry** 并显示以十六进制表示的键，以便轻松地对原始 **ARRAY** 进行双重检查。 名称以 **show** 开头的每个方法都会重载两个版本，其中一个版本采用 **count** 参数来指示要显示的元素数量，第二个版本显示序列中的所有元素。
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这里是一个基本的测试：
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```java
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// collectiontopics/HTMLColorTest.java
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import static onjava.HTMLColors.*;
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public class HTMLColorTest {
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static final int DISPLAY_SIZE = 20;
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public static void main(String[] args) {
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show(MAP, DISPLAY_SIZE);
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border();
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showInv(INVMAP, DISPLAY_SIZE);
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border();
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show(LIST, DISPLAY_SIZE);
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border();
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showrgb(RGBLIST, DISPLAY_SIZE);
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}
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}
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/* Output:
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0xF0F8FF: AliceBlue
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0xFAEBD7: AntiqueWhite
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0x7FFFD4: Aquamarine
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0xF0FFFF: Azure
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0xF5F5DC: Beige
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0xFFE4C4: Bisque
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0x000000: Black
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0xFFEBCD: BlanchedAlmond
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0x0000FF: Blue
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0x8A2BE2: BlueViolet
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0xA52A2A: Brown
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0xDEB887: BurlyWood
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0x5F9EA0: CadetBlue
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0x7FFF00: Chartreuse
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0xD2691E: Chocolate
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0xFF7F50: Coral
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0x6495ED: CornflowerBlue
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0xFFF8DC: Cornsilk
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0xDC143C: Crimson
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0x00FFFF: Cyan
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******************************
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AliceBlue 0xF0F8FF
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AntiqueWhite 0xFAEBD7
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Aquamarine 0x7FFFD4
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Azure 0xF0FFFF
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Beige 0xF5F5DC
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Bisque 0xFFE4C4
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Black 0x000000
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BlanchedAlmond 0xFFEBCD
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Blue 0x0000FF
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BlueViolet 0x8A2BE2
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Brown 0xA52A2A
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BurlyWood 0xDEB887
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CadetBlue 0x5F9EA0
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Chartreuse 0x7FFF00
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Chocolate 0xD2691E
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Coral 0xFF7F50
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CornflowerBlue 0x6495ED
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Cornsilk 0xFFF8DC
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Crimson 0xDC143C
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Cyan 0x00FFFF
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******************************
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AliceBlue
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AntiqueWhite
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Aquamarine
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Azure
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Beige
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Bisque
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Black
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BlanchedAlmond
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Blue
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BlueViolet
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Brown
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BurlyWood
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CadetBlue
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Chartreuse
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Chocolate
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Coral
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CornflowerBlue
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Cornsilk
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Crimson
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Cyan
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******************************
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0xF0F8FF
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0xFAEBD7
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0x7FFFD4
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0xF0FFFF
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0xF5F5DC
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0xFFE4C4
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0x000000
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0xFFEBCD
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0x0000FF
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0x8A2BE2
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0xA52A2A
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0xDEB887
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0x5F9EA0
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0x7FFF00
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0xD2691E
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0xFF7F50
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0x6495ED
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0xFFF8DC
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0xDC143C
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0x00FFFF
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*/
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```
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可以看到，使用 **LinkedHashMap** 确实能够保留 **HTMLColors.ARRAY** 的顺序。
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<!-- List Behavior -->
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## List表现
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<!-- Set Behavior -->
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## Set表现
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<!-- Using Functional Operations with any Map -->
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## 在Map中使用函数式操作
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<!-- Selecting Parts of a Map -->
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## 选择Map的部分
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<!-- Filling Collections -->
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## 集合的fill方法
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<!-- Custom Collection and Map using Flyweight -->
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## 使用Flyweight自定义集合和Map
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<!-- Collection Functionality -->
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## 集合功能
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<!-- Optional Operations -->
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## 可选操作
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<!-- Sets and Storage Order -->
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## Set和存储顺序
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<!-- Queues -->
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## 队列
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<!-- Understanding Maps -->
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## 理解Map
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<!-- Utilities -->
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## 集合工具类
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<!-- Holding References -->
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## 持有引用
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<!-- Java 1.0/1.1 Collections -->
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## 避免旧式类库
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<!-- Summary -->
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## 本章小结
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<!-- 分页 -->
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<div style="page-break-after: always;"></div> |