Java 中的 TreeMap ceilingEntry()和 ceilingKey()方法
原文:https://www . geesforgeks . org/tree map-ceilingentry-and-ceiling key-methods-in-Java/
Java.util.TreeMap 中有两个 ceilingEntry()的变体，本文将对这两个变体进行讨论。
*1。ceilingEntry(K 键):*用于返回与大于或等于给定键的最小键相关联的键值映射，如果没有这样的键，则返回或 null。
**Syntax :**
**public Map.Entry ceilingEntry(K key)**
**Parameters :**
**key :** The key to be matched.
**Return Value :**
It returns the entry with the least key greater than or equal to key, and null if
there is no such key.
**Exception :**
**ClassCastException :** It throws the exception if the specified key cannot be compared
with the keys currently in the map.
**NullPointerException :** It throws the exception if the specified key is null.
// Java code to demonstrate the working of
// ceilingEntry()
import java.io.*;
import java.util.*;
public class ceilingEntry1 {
public static void main(String[] args) {
// Declaring the tree map of Integer and String
TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
treemap.put(2, "two");
treemap.put(7, "seven");
treemap.put(3, "three");
// Use of ceilingEntry()
// returns 7=seven ( next greater key-value)
System.out.println("The next greater key-value of 5 is : " + treemap.ceilingEntry(5));
// returns "null" as no value present
// greater than or equal to number
System.out.println("The next greater key-value of 8 is : " + treemap.ceilingEntry(8));
}
}
输出:
The next greater key-value of 5 is : 7=seven
The next greater key-value of 8 is : null
*2。ceilingKey(K key) :* 这个也和上面那个有相同的工作，但是唯一的区别是它不包含映射键。它只返回大于或等于给定键的最小键，否则返回空值。
**Syntax :**
public K ceilingKey(K key)
**Parameters :**
**key :** The key to be matched.
**Return Value :**
It returns the entry with the least key greater than or equal to key, and null
if there is no such key.
**Exception:**
**ClassCastException :** It throws the exception if the specified key cannot be compared
with the keys currently in the map.
**NullPointerException :** It throws the exception if the specified key is null.
// Java code to demonstrate the working of
// ceilingKey()
import java.io.*;
import java.util.*;
public class ceilingKey1 {
public static void main(String[] args) {
// Declaring the tree map of Integer and String
TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
treemap.put(2, "two");
treemap.put(7, "seven");
treemap.put(3, "three");
// Use of ceilingKey()
// returns 7 ( next greater key)
System.out.println("The next greater key of 5 is : " + treemap.ceilingKey(5));
// returns "null" as no key present
// greater than or equal to number
System.out.println("The next greater key of 8 is : " + treemap.ceilingKey(8));
}
}
输出:
The next greater key of 5 is : 7
The next greater key of 8 is : null
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