Java Collections emptyNavigableMap()
Java集合类的
emptyNavigableMap()方法返回一个不变的空可导航地图。
语法
以下是
emptyNavigableMap()方法的声明:
public static final <K,V> NavigableMap<K,V> emptyNavigableMap()
参数
此方法不接受任何参数。
返回
emptyNavigableMap()方法返回一个空的不可变的可导航地图。
异常
NA
兼容版本
Java 1.8及更高版本
示例1
import java.util.*;
public class CollectionsEmptyNavigableMapExample1 {
public static void main(String[] args) {
//Create an empty Map
NavigableMap<String,String> EmptyNavMap = Collections.emptyNavigableMap</span>();
System.out.println("Created Empty Navigable Map: "+EmptyNavMap);
}
}
输出:
Created Empty Navigable Map: {}
示例2
import java.util.*;
public class CollectionsEmptyNavigableMapExample2 {
public static void main(String[] args) {
//Create an empty Map
NavigableMap<String,String> EmptyNavMap = Collections.emptyNavigableMap</span>();
System.out.println("Created Empty Navigable Map: "+EmptyNavMap);
// try to add elements
EmptyNavMap.put("1","from lidihuo.com");
}
}
输出:
Created Empty Navigable Map: {}
Exception in thread "main" java.lang.UnsupportedOperationException
at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
at myPackage.CollectionsEmptyNavigableMapExample2.main(CollectionsEmptyNavigableMapExample2.java:9)
示例3
import java.util.*;
public class CollectionsEmptyNavigableMapExample3 {
public static void main(String[] args) {
//Create an empty Map
NavigableMap<Integer, Integer> empNavMap = Collections.emptyNavigableMap</span>();
empNavMap.put(1, 23424);
empNavMap.put(2, 65776);
System.out.println("Created empty immutable Navigable Map: "+empNavMap);
}
}
输出:
Exception in thread "main" java.lang.UnsupportedOperationException
at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
at myPackage.CollectionsEmptyNavigableMapExample3.main(CollectionsEmptyNavigableMapExample3.java:7)
