java treemap

TreeMap類(lèi)的keySet()方法 (TreeMap Class keySet() method)

• keySet() method is available in java.util package.

  keySet()方法在java.util包中可用。

• keySet() method is used to return a set of keys that exists in this TreeMap to be viewed in a Set.

  keySet()方法用于返回此TreeMap中存在的一組鍵，以便在Set中進(jìn)行查看。

• keySet() 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.

  keySet()方法是一種非靜態(tài)方法，只能通過(guò)類(lèi)對(duì)象訪問(wèn)，如果嘗試使用類(lèi)名訪問(wèn)該方法，則會(huì)收到錯(cuò)誤消息。

• keySet() method does not throw an exception at the time of returning the key set.

  返回鍵集時(shí)， keySet()方法不會(huì)引發(fā)異常。

Syntax:

句法：

public Set keySet();

Parameter(s):

參數(shù)：

• It does not accept any parameter.

  它不接受任何參數(shù)。

Return value:

返回值：

The return type of the method is Set, it returns contained set of keys in this TreeMap to be viewed in a Set.

方法的返回類(lèi)型為Set ，它返回此TreeMap中包含的鍵集，以在Set中查看。

Example:

例：

// Java program to demonstrate the example // of Set keySet() method of TreeMap import java.util.*;public class KeySetOfTreeMap {public static void main(String[] args) {// Instantiates TreeMapTreeMap < Integer, String > tm = new TreeMap < Integer, String > ();// By using put() method is// to put the key-value pairs in// treemap tmtm.put(1, "C");tm.put(4, "C++");tm.put(3, "Java");tm.put(2, "Php");// Display TreeMap tmSystem.out.println("tm: " + tm);// By using keySet() method is to// return the set of keys to be// viewed in a SetSet s = tm.keySet();// Display set view of TreeMapSystem.out.println("tm.keySet(): " + s);} }

Output

輸出量

tm: {1=C, 2=Php, 3=Java, 4=C++} tm.keySet(): [1, 2, 3, 4]

翻譯自: https://www.includehelp.com/java/treemap-keyset-method-with-example.aspx

java treemap

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