Java TreeMap.floorEntry()、floorKey()用法及代码示例

在许多地方都使用找到小于给定值的最大数，而将其放在基于Map的容器中始终是加号。 Java.util.TreeMap也使用floor()函数提供此函数。有2个变体，下面都会讨论。

1. floorEntry()：它返回与小于或等于给定键的最大键关联的键值映射，如果没有这样的键，则返回null。

参数：
key:This is the key to be matched.
返回值：
It returns an entry with the greatest key less than or equal to key,
or null if there is no such key.
Exception:
ClassCastException:This exception is thrown if the specified
key cannot be compared with the keys currently in the map.
NullPointerException :This exception is thrown if the specified
key is null and this map uses natural ordering, or its comparator does not permit null keys.

// Java code to demonstrate the working 
// of floorEntry() 
import java.io.*; 
import java.util.*; 
public class floorEntry { 
    public static void main(String[] args) 
    { 
  
        // Declaring the tree map of Integer and String 
        TreeMap<Integer, String> tmp = new TreeMap<Integer, String>(); 
  
        // assigning the values in the tree map 
        // using put() 
        tmp.put(10, "ten"); 
        tmp.put(7, "seven"); 
        tmp.put(19, "nineteen"); 
        tmp.put(3, "three"); 
  
        // use of floorEntry() 
        // displays the floor value of 6 
        // prints 3=three 
        System.out.println("The greatest key-value less than 6 is:" 
        + tmp.floorEntry(6)); 
    } 
}

输出：

The greatest key-value less than 6 is:3=three

2. floorKey()：它返回小于或等于给定键的最大键；如果没有这样的键，则返回null。

参数：
key:This is the key to be matched.
返回值：
It returns an entry with the greatest key less than or equal to key, or
null if there is no such key.
Exception:
ClassCastException:This exception is thrown if the specified
key cannot be compared with the keys currently in the map.
NullPointerException :This exception is thrown if the specified key
is null and this map uses natural ordering, or its comparator does not permit null keys.

// Java code to demonstrate the working 
// of floorKey() 
import java.io.*; 
import java.util.*; 
public class floorKey { 
    public static void main(String[] args) 
    { 
  
        // Declaring the tree map of Integer and String 
        TreeMap<Integer, String> tmp = new TreeMap<Integer, String>(); 
  
        // assigning the values in the tree map 
        // using put() 
        tmp.put(10, "ten"); 
        tmp.put(7, "seven"); 
        tmp.put(19, "nineteen"); 
        tmp.put(3, "three"); 
  
        // use of floorKey() 
        // displays the floor key of 
        // prints 3 
        System.out.println("The greatest key less than 6 is:"
        + tmp.floorKey(6)); 
    } 
}

输出：

The greatest key less than 6 is:3

实际应用：该函数的可能应用很多。从最大距离开始使用给定的汽油或使用给定成分的可能菜肴。前一个在下面的代码中讨论。

// Java code to demonstrate the application 
// of floorKey() and floorEntry 
import java.io.*; 
import java.util.*; 
public class floorappli { 
    public static void main(String[] args) 
    { 
  
        // Declaring the tree map of Integer and String 
        TreeMap<Integer, String> destin = new TreeMap<Integer, String>(); 
  
        // assigning the km with destination 
        // from beginning 
        // using put() 
        destin.put(10, "Delhi"); 
        destin.put(7, "Gurgaon"); 
        destin.put(19, "Noida"); 
        destin.put(3, "Ring Road"); 
  
        // Entering the available Petrol (consider 1km/litre) 
        int petr = 12; 
  
        // Maximum place you can reach 
        System.out.println("The maximum place you can reach with given petrol:"
        + destin.floorEntry(petr)); 
    } 
}

输出：

The maximum place you can reach with given petrol:10=Delhi

相关用法

注：本文由纯净天空筛选整理自Shambhavi Singh 1大神的英文原创作品 Java.util.TreeMap.floorEntry() and floorKey() in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。