java treemap

TreeMap类的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中存在的一组键，以便在Set中进行查看。

• 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()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

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

  返回键集时， keySet()方法不会引发异常。

Syntax:

句法：

    public Set keySet();

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 Set, it returns contained set of keys in this TreeMap to be viewed in a Set.

方法的返回类型为Set ，它返回此TreeMap中包含的键集，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 TreeMap
TreeMap < Integer, String > tm = new TreeMap < Integer, String > ();
// By using put() method is
// to put the key-value pairs in
// treemap tm
tm.put(1, "C");
tm.put(4, "C++");
tm.put(3, "Java");
tm.put(2, "Php");
// Display TreeMap tm
System.out.println("tm: " + tm);
// By using keySet() method is to
// return the set of keys to be
// viewed in a Set
Set s = tm.keySet();
// Display set view of TreeMap
System.out.println("tm.keySet(): " + s);
}
}

Output

输出量

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

翻译自: https://www.includehelp.com/java/treemap-keyset-method-with-example.aspx

java treemap