Java 安全地使类型或方法能够对各种类型的对象进行操作
安全地使类型或方法能够对各种类型的对象进行操作
实例源码：
源代码：
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/* 2
来自 3
*时代Java - N o w J a v a . c o m*/4
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import java.util.ArrayList;6
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import java.util.HashMap;8
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import java.util.List;10
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import java.util.Map;12
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public class Main {15
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public static void main(String[] args) {17
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List<Player> team = new ArrayList<>();19
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Player player1 = new Player("A", "AA", 5);21
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Player player2 = new Player("B", "BB", 15);23
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Player player3 = new Player("C", "CC", 1);25
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Player player4 = new Player("D", "DD", 18);27
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Player player5 = new Player("E", "EE", 7);29
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team.add(player1);32
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team.add(player2);34
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team.add(player3);36
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team.add(player4);38
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team.add(player5);40
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List objectList = new ArrayList();/* 来自 nowjava.com*/43
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Object obj1 = "none";45
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objectList.add(obj1);47
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// Create a List that can be of type that is any superclass of Player50
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List<? super Player> myTeam = objectList;52
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for (Object p : myTeam) {54
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System.out.println("Printing the objects...");56
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System.out.println(p.toString());58
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}60
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Map<String, String> strMap = new HashMap<>();63
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strMap.put("first", "Josh");65
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strMap.put("last", "Juneau");67
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System.out.println(strMap.values());69
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}71
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}73
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class Player {76
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private String firstName = null;79
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private String lastName = null;81
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private String position = null;83
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private int status = -1;85
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private int goals;87
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public Player() {90
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}93
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public Player(String position, int status) {96
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this.position = position;98
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this.status = status;100
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}102
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public Player(String first, String last, int goals) {105
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this.firstName = first;107
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this.lastName = last;109
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this.goals = goals;111
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}113
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public Player(String position, int status, String first, String last) {116
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this.position = position;118
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this.status = status;120
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this.firstName = first;122
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this.lastName = last;124
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}126
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public String playerString() {129
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return getFirstName() + " " + getLastName() + " - " + getPosition();131
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}133
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/**136
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* @return the firstName138
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*/140
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public String getFirstName() {142
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return firstName;144
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}146
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/**149
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* @param firstName151
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* the firstName to set153
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*/155
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public void setFirstName(String firstName) {157
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this.firstName = firstName;159
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}161
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/**164
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* @return the lastName166
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*/168
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public String getLastName() {170
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return lastName;172
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}174
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/**177
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* @param lastName179
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* the lastName to set181
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*/183
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public void setLastName(String lastName) {185
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this.lastName = lastName;187
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}189
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/**192
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* @return the position194
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*/196
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public String getPosition() {198
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return position;200
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}202
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/**205
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* @param position207
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* the position to set209
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*/211
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public void setPosition(String position) {213
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