Java TreeMap.floorEntry()、floorKey()用法及代碼示例

在許多地方都使用找到小於給定值的最大數，而將其放在基於Map的容器中始終是加號。 Java.util.TreeMap也使用floor()函數提供此函數。有2個變體，下麵都會討論。

1. floorEntry()：它返回與小於或等於給定鍵的最大鍵關聯的鍵值映射，如果沒有這樣的鍵，則返回null。

參數：
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)); 
    } 
}

輸出：

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

2. floorKey()：它返回小於或等於給定鍵的最大鍵；如果沒有這樣的鍵，則返回null。

參數：
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)); 
    } 
}

輸出：

The greatest key less than 6 is:3

實際應用：該函數的可能應用很多。從最大距離開始使用給定的汽油或使用給定成分的可能菜肴。前一個在下麵的代碼中討論。

// 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)); 
    } 
}

輸出：

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

相關用法

注：本文由純淨天空篩選整理自Shambhavi Singh 1大神的英文原創作品 Java.util.TreeMap.floorEntry() and floorKey() in Java。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。