Java NavigableMap Interface用法及代碼示例

// Java program to demonstrate 
// the NavigableMap interface 
import java.util.NavigableMap; 
import java.util.TreeMap; 
  
public class NavigableMapExample { 
  
    public static void main(String[] args) 
    { 
        // Instantiate an object 
        // Since NavigableMap 
        // is an interface so we 
        // use TreeMap 
        NavigableMap<String, Integer> nm 
            = new TreeMap<String, Integer>(); 
  
        // Add elements using put() method 
        nm.put("C", 888); 
        nm.put("Y", 999); 
        nm.put("A", 444); 
        nm.put("T", 555); 
        nm.put("B", 666); 
        nm.put("A", 555); 
  
        // Print the contents on the console 
        System.out.println("Mappings of NavigableMap : "
                           + nm); 
  
        System.out.printf("Descending Set  : %s%n", 
                          nm.descendingKeySet()); 
        System.out.printf("Floor Entry  : %s%n", 
                          nm.floorEntry("L")); 
        System.out.printf("First Entry  : %s%n", 
                          nm.firstEntry()); 
        System.out.printf("Last Key : %s%n", nm.lastKey()); 
        System.out.printf("First Key : %s%n", 
                          nm.firstKey()); 
        System.out.printf("Original Map : %s%n", nm); 
        System.out.printf("Reverse Map : %s%n", 
                          nm.descendingMap()); 
    } 
}

// Java program for adding elements 
// to a NavigableMap 
import java.util.*; 
  
class AddingElementsExample { 
    public static void main(String args[]) 
    { 
  
        // Instantiate an object 
        // Since NavigableMap is an interface 
        // We use TreeMap 
        NavigableMap<Integer, String> nmap 
            = new TreeMap<Integer, String>(); 
  
        // Add elements using put() 
        nmap.put(3, "Geeks"); 
        nmap.put(2, "For"); 
        nmap.put(1, "Geeks"); 
  
        // Print the contents on the console 
        System.out.println("Mappings of NavigableMap : "
                           + nmap); 
    } 
}

// Java Program for deleting 
// elements from NavigableMap 
import java.util.*; 
  
class RemovingElementsExample { 
    
    public static void main(String args[]) 
    { 
        // Instantiate an object 
        // Since NavigableMap 
        // is an interface 
        // We use TreeMap 
        NavigableMap<Integer, String> nmap 
            = new TreeMap<Integer, String>(); 
  
        // Add elements using put() 
        nmap.put(3, "Geeks"); 
        nmap.put(2, "Geeks"); 
        nmap.put(1, "Geeks"); 
        nmap.put(4, "For"); 
  
        // Print the contents on the console 
        System.out.println("Mappings of NavigableMap : "
                           + nmap); 
  
        // Remove elements using remove() 
        nmap.remove(4); 
  
        // Print the contents on the console 
        System.out.println( 
            "\nNavigableMap, after remove operation : "
            + nmap); 
  
        // Clear the entire map using clear() 
        nmap.clear(); 
        System.out.println( 
            "\nNavigableMap, after clear operation : "
            + nmap); 
    } 
}

// Java Program for accessing 
// elements in a NavigableMap 
  
import java.util.*; 
  
public class AccessingElementsExample { 
  
    public static void main(String[] args) 
    { 
        // Instantiate an object 
        // Since NavigableMap is an interface 
        // We use TreeMap 
        NavigableMap<Integer, String> nmap 
            = new TreeMap<Integer, String>(); 
  
        // Add elements using put() 
        nmap.put(8, "Third"); 
        nmap.put(6, "Second"); 
        nmap.put(3, "First"); 
        nmap.put(11, "Fourth"); 
  
        // Accessing the elements using get() 
        // with key as a parameter 
        System.out.println(nmap.get(3)); 
        System.out.println(nmap.get(6)); 
        System.out.println(nmap.get(8)); 
        System.out.println(nmap.get(11)); 
  
        // Display the set of keys using keySet() 
        System.out.println("\nThe NavigableMap key set: "
                           + nmap.keySet()); 
    } 
}

// Java Program for traversing 
// a NavigableMap 
import java.util.*; 
  
class TraversalExample { 
    
    public static void main(String args[]) 
    { 
        // Instantiate an object 
        // Since NavigableMap is an interface 
        // We use TreeMap 
        NavigableMap<Integer, String> nmap 
            = new TreeMap<Integer, String>(); 
  
        // Add elements using put() 
        nmap.put(3, "Geeks"); 
        nmap.put(2, "For"); 
        nmap.put(1, "Geeks"); 
  
        // Create an Iterator over the 
        // NavigableMap 
        Iterator<NavigableMap.Entry<Integer, String> > itr 
            = nmap.entrySet().iterator(); 
  
        System.out.println("Traversing using Iterator: "); 
        // The hasNext() method is used to check if there is 
        // a next element The next() method is used to 
        // retrieve the next element 
        while (itr.hasNext()) { 
            NavigableMap.Entry<Integer, String> entry 
                = itr.next(); 
            System.out.println("Key = " + entry.getKey() 
                               + ", Value = "
                               + entry.getValue()); 
        } 
  
        System.out.println("Traversing using for-each: "); 
        // Iterate using for-each loop 
        for (Map.Entry mapElement : nmap.entrySet()) { 
            // get the key using getKey() 
            int key = (int)mapElement.getKey(); 
  
            // Finding the value 
            String value = (String)mapElement.getValue(); 
  
            System.out.println("Key = " + key 
                               + ", Value = " + value); 
        } 
    } 
}