• Tags
  •         
  • www.breakyizhan.com
  •    

    Java中的java.util.TreeMap.tailMap(from_Key)方法用于获取映射的部分或视图,其键大于等于参数中的from_key。在一个map中进行的任何更改都将反映另一个map中的更改。

    句法:

    Tree_Map.tailMap(from_Key)

    参数:该方法从TreeMap中获取Key类型的一个参数from_key,并引用设置为低于其返回其映射的低点的键。

    返回值:该方法返回其键大于from_Key的映射部分。

    例外:该方法抛出三种类型的异常:

    • ClassCastException:如果方法中提到的参数无法与此映射的键进行比较,则抛出此异常。
    • NullPointerException:如果其中一个参数为null类型且map不接受任何null值,则抛出此异常。
    • IllegalArgumentException:如果提到的参数超出范围,则抛出此异常。

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

    程序1:

    // Java code to illustrate the tailMap() 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 original map is: "
                               + tree_map);
    
            // Displaying the submap
            System.out.println("The tailMap is " + tree_map.tailMap(15));
        }
    }
    
    输出:

    The original map is: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
    The tailMap is {15=4, 20=Geeks, 25=Welcomes, 30=You}

    程序2:

    // Java code to illustrate the tailMap() 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 original map is: "
                               + tree_map);
    
            // Displaying the tailMap
            System.out.println("The tailMap is " + tree_map.tailMap("Geeks"));
        }
    }
    

    输出:

    The original map is: {4=15, Geeks=20, Welcomes=25, You=30}
    The tailMap is {Geeks=20, Welcomes=25, You=30}

    程序3:默认情况下,from_key包含在tail_Map中。如果需要忽略或排除,则可以将另一个参数与from_key一起传递,这是false

    // Java code to illustrate the tailMap() 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 original map is: "
                               + tree_map);
    
            // Displaying the tailMap
            System.out.println("The tailMap is " + tree_map.tailMap("Geeks", false));
        }
    }
    

    输出:

    The original map is: {4=15, Geeks=20, Welcomes=25, You=30}
    The tailMap is {Welcomes=25, You=30}

     
    转载请保留页面地址:https://www.breakyizhan.com/java/5509.html