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  • 2018-09-17  08:41:37        
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    java.util.TreeMap.lastKey()用于检索映射中存在的最后一个或最高密钥。

    句法:

     tree_map.lastKey()

    参数:该方法不接受任何参数。

    返回值:该方法返回地图中的最后一个键。

    异常:如果映射为空,则该方法抛出NoSuchElementException

    下面的程序说明了java.util.TreeMap.lastKey()方法的工作原理

    程序1:

    // Java code to illustrate the lastKey() method
    import java.util.*;
      
    public class Tree_Map_Demo {
        public static void main(String[] args)
        {
      
            // Creating an empty TreeMap
            TreeMap<Integer, String> tree_map = new TreeMap<Integer, String>(); 
      
            // Mapping string values to int keys
            tree_map.put(10, "Geeks");
            tree_map.put(15, "4");
            tree_map.put(20, "Geeks");
            tree_map.put(25, "Welcomes");
            tree_map.put(30, "You");
      
            // Displaying the TreeMap
            System.out.println("The Mappings are: " + tree_map);
      
            // Displaying the lastKey of the map
            System.out.println("The last key is " + tree_map.lastKey());
        }
    }
    

    输出:

    The Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
    The last key is 30

    程序2:

    // Java code to illustrate the lastKey() method
    import java.util.*;
     
    public class Tree_Map_Demo {
        public static void main(String[] args)
        {
     
            // Creating an empty TreeMap
            TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>(); 
     
            // Mapping int values to string keys
            tree_map.put("Geeks", 10);
            tree_map.put("4", 15);
            tree_map.put("Geeks", 20);
            tree_map.put("Welcomes", 25);
            tree_map.put("You", 30);
     
            // Displaying the TreeMap
            System.out.println("The Mappings are: " + tree_map);
     
            // Displaying the lastKey of the map
            System.out.println("The last key is " + tree_map.lastKey());
        }
    }
    

    输出:

    The Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
    The last key is You

     
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