Java EnumMap keySet()
Java EnumMap类的
keySet()方法用于获取包含在地图。此方法以自然顺序(声明枚举常量的顺序)返回一组键。
语法
参数
NA
返回
此方法返回包含在枚举映射。
异常
NA
示例1
import java.util.*;
public class EnumMapKeySetExample1 {
// create an enum
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);
Set<Tutorial> set = map.keySet();
System.out.println("KeySet: "+set);
}
}
输出:
Map: {CSS=1, Python=2, PHP=3, Java=4}
KeySet: [CSS, Python, PHP, Java]
示例2
import java.util.*;
public class EnumMapKeySetExample2 {
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);
Set<Days> set = map.keySet();
System.out.println("KeySet: "+set);
}
}
输出:
Map: {Monday=1, Tuesday=2, Wednesday=3}
KeySet: [Monday, Tuesday, Wednesday]
示例3
import java.util.*;
public class EnumMapKeySetExample3 {
// 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);
Set<Months> set = map.keySet();
System.out.println("KeySet: "+set);
}
}
输出:
Map: {January=1, February=2, March=3, April=4}
KeySet: [January, February, March, April]
