treeset java_Java TreeSet first（）方法与示例

「爱情、让人受尽委屈。」 2023-03-05 12:53 3阅读 0赞

treeset java

## TreeSet类的first()方法 **(**TreeSet Class first() method**)** ##

*  **first() method** is available in java.util package.
    
    **first()方法**在java.util包中可用。
 *  **first() method** is used to retrieve the first lowest element in this TreeSet.
    
    **first()方法**用于检索此TreeSet中的第一个最低元素。
 *  **first() method** is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
    
    **first()方法**是一个非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。
 *  **first() method** may throw an exception at the time of returning the first least object in this TreeSet.
    
    返回此TreeSet中的第一个最小对象时， **first()方法**可能会引发异常。
    
    NoSuchElementException – This exception may throw when this TreeSet is “blank”.
    
    NoSuchElementException-如果此TreeSet为“空白”，则可能引发此异常。

**Syntax:**

**句法：**

public Element first();

**Parameter(s):**

**参数：**

*  It does not accept any parameter.
    
    它不接受任何参数。

**Return value:**

**返回值：**

The return type of the method is Element, it gets the first least element exists in this TreeSet.

方法的返回类型为Element ，它获取此TreeSet中存在的第一个最小元素。

**Example:**

**例：**

// Java program to demonstrate the example 
    // of Element first() method of TreeSet 
    
    import java.util.*;
    
    public class FirstOfTreeSet {
        
        public static void main(String[] args) {
        
            // Instantiates a TreeSet object
            TreeSet < String > tree_set = new TreeSet < String > ();
    
            // By using add() method is to add
            // the given object of this TreeSet 
            tree_set.add("C");
            tree_set.add("C++");
            tree_set.add("JAVA");
            tree_set.add("PHP");
            tree_set.add("SFDC");
    
            // Display TreeSet
            System.out.println("TreeSet: " + tree_set);
    
            // By using first() method is to return
            // the first least element exists in this TreeSet
            Object first_least = tree_set.first();
    
            // Display first_least
            System.out.println("tree_set.first(): " + first_least);
        }
    }

**Output**

**输出量**

TreeSet: [C, C++, JAVA, PHP, SFDC]
    tree_set.first(): C

> 翻译自: [https://www.includehelp.com/java/treeset-first-method-with-example.aspx][https_www.includehelp.com_java_treeset-first-method-with-example.aspx]

treeset java

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