Java Collections emptySortedMap()
Java集合类的
emptySortedMap()方法返回一个不可变的空排序映射。
语法
以下是
emptySortedMap()方法的声明:
public static final <K,V> SortedMap<K,V> emptySortedMap()
参数
此方法不接受任何参数。
返回
emptySortedMap()方法返回一个空的不可变的已排序映射。
异常
NA
兼容版本
Java 1.8及更高版本
示例1
import java.util.*;
public class CollectionsEmptySortedMapExample1 {
public static void main(String[] args) {
SortedMap<String,String> EmpSortedMap = Collections.emptySortedMap</span>();
System.out.println("Created Empty Sorted Map: "+EmpSortedMap);
}
}
输出:
Created Empty Sorted Map: {}
示例2
import java.util.*;
public class CollectionsEmptySortedMapExample2 {
public static void main(String[] args) {
SortedMap<String,String> EmpSortedMap = Collections.emptySortedMap</span>();
System.out.println("Created Empty Sorted Map: "+EmpSortedMap);
// try to add elements
EmpSortedMap.put("1","from lidihuo.com");
}
}
输出:
Created Empty Sorted Map: {}
Exception in thread "main" java.lang.UnsupportedOperationException
at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
at myPackage.CollectionsEmptySortedMapExample2.main(CollectionsEmptySortedMapExample2.java:9)
示例3
import java.util.*;
public class CollectionsEmptySortedMapExample3 {
public static void main(String[] args) {
//Create an empty Map
SortedMap<Integer, Integer> empSortedMap = Collections.emptySortedMap</span>();
empSortedMap.put(1, 23424);
empSortedMap.put(2, 65776);
System.out.println("Created empty immutable Sorted Map: "+empSortedMap);
}
}
输出:
Exception in thread "main" java.lang.UnsupportedOperationException
at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
at myPackage.CollectionsEmptySortedMapExample3.main(CollectionsEmptySortedMapExample3.java:8)
