Java中的 EnumMap containsKey() 方法
Java.util.EnumMap.containsKey( key ) 方法用于检查参数中提到的指定键是否存在于此映射中。
句法:
boolean containsKey(Object key)
参数:该方法接受一个参数键,该键是指要验证的键。
返回值:如果 EnumMap 中存在键,则该方法返回 true,否则返回 false。
下面的程序说明了 containsKey() 方法:
方案一:
// Java program to demonstrate containsKey() method
import java.util.*;
// An enum of gfg visitors is created
public enum gfg_visitors {
India,
United_States,
China,
Japan,
Canada
};
class Enum_map {
public static void main(String[] args)
{
EnumMap mp = new
EnumMap(gfg_visitors.class);
// values are associated in mp
mp.put(gfg_visitors.India, "61.4%");
mp.put(gfg_visitors.United_States, "18.4%");
mp.put(gfg_visitors.China, "2.5%");
mp.put(gfg_visitors.Japan, "1.1%");
mp.put(gfg_visitors.Canada, "1.1%");
// Check if map contains gfg visitor from United_States
boolean ans = mp.containsKey(gfg_visitors.United_States);
// Prints the result
System.out.println("gfg_visitors from United States: " + ans);
}
}
输出:
gfg_visitors from United States: true
方案二:
// Java program to demonstrate containsKey() method
import java.util.*;
// An enum of gfg visitors is created
public enum gfg_visitors {
India,
United_States,
China,
Japan,
Canada,
Russia
};
class Enum_map {
public static void main(String[] args)
{
EnumMap mp = new
EnumMap(gfg_visitors.class);
// values are associated in mp
mp.put(gfg_visitors.India, "61.4%");
mp.put(gfg_visitors.United_States, "18.4%");
mp.put(gfg_visitors.China, "2.5%");
mp.put(gfg_visitors.Japan, "1.1%");
mp.put(gfg_visitors.Canada, "1.1%");
// check if map contains gfg visitor from Russia
boolean ans = mp.containsKey(gfg_visitors.Russia);
// prints the result
System.out.println("gfg_visitors from Russia: " + ans);
}
}
输出:
gfg_visitors from Russia: false