Java EnumMap get()
Java EnumMap类的
get()方法用于获取指定键的映射值。
语法
参数
key-要返回其关联值的键
返回
此方法返回指定键所映射到的值。
如果此映射不包含键的映射,则此方法返回null。
如果此映射包含从键k到值v的映射(例如(key == k)),则此方法返回v。
异常
NA
示例1
import java.util.*;
public class EnumMapGetExample1 {
public enum Tutorial {
CSS, Python, PHP, Java, Javascript
};
public static void main(String[] args) {
EnumMap<Tutorial, String>map =new EnumMap<Tutorial, String>(Tutorial.class);
map.put(Tutorial.CSS, "1");
map.put(Tutorial.Python, "2");
map.put(Tutorial.PHP, "3");
map.put(Tutorial.Java, "4");
System.out.println("Map: "+map);
String value = map.get(Tutorial.CSS);
System.out.println("Tutorial.CSS value: "+value);
System.out.println("Tutorial.Javascript value: "+ map.get(Tutorial.Javascript));
}
}
输出:
Map: {CSS=1, Python=2, PHP=3, Java=4}
Tutorial.CSS value: 1
Tutorial.Javascript value: null
示例2
import java.util.*;
public class EnumMapGetExample2 {
// create an enum
public enum Days {
Monday, Tuesday, Wednesday, Thursday
};
public static void main(String[] args) {
EnumMap<Days, String> map= new EnumMap<Days, String>(Days.class);
map.put(Days.Monday,"1");
map.put(Days.Tuesday,"2");
map.put(Days.Wednesday,"3");
System.out.println("Map: "+map);
String value = map.get(Days.Monday);
System.out.println("Days.Monday value: "+value);
System.out.println("Days.Thursday value: "+map.get(Days.Thursday));
}
}
输出:
Map: {Monday=1, Tuesday=2, Wednesday=3}
Days.Monday value: 1
Days.Thursday value: null
示例3
import java.util.*;
public class EnumMapGetExample3 {
// create an enum
public enum Months {
January, February, March, April, May
}
;
public static void main(String[] args) {
EnumMap<Months, String> map = new EnumMap<Months, String>(Months.class);
map.put(Months.January,"1");
map.put(Months.February,"2");
map.put(Months.March,"3");
map.put(Months.April,"4");
System.out.println("Map: "+map);
String value = map.get(Months.March);
System.out.println("Months.March value: "+value);
System.out.println("Months.May value: "+map.get(Months.May));
}
}
输出:
Map: {January=1, February=2, March=3, April=4}
Months.March value: 3
Months.May value: null