Java Collections checkedSet()方法及示例

java.util.Collections 类的 checkedSet() 方法用于返回指定集合的动态类型安全视图。如果指定的集合是可序列化的，那么返回的集合将是可序列化的。

因为null被认为是任何引用类型的值，所以只要支持的集合允许插入null元素。

语法:

public static  Set checkedSet(Set s, Class type)

参数： 该方法接受以下参数作为参数

• s： 要返回的动态类型安全视图的集合
• type： s允许持有的元素的类型。

返回值： 该方法返回指定集合的动态 类型安全视图
以下是说明checkedSet()方法的例子

例1：

// Java program to demonstrate
// checkedSet() method
// for String value
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        try {
 
            // creating object of Set<String>
            Set<String> hset = new TreeSet<String>();
 
            // Adding element to hmap
            hset.add("Ram");
            hset.add("Gopal");
            hset.add("Verma");
 
            // print the set
            System.out.println("Set: " + hset);
 
            // create typesafe view of the specified set
            Set<String>
                tsset = Collections
                            .checkedSet(hset, String.class);
 
            // printing the typesafe view of specified list
            System.out.println("Typesafe view of Set: "
                               + tsset);
        }
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

Set: [Gopal, Ram, Verma]
Typesafe view of Set: [Gopal, Ram, Verma]

例2：

// Java program to demonstrate
// checkedSet() method
// for Integer value
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
 
            // creating object of Set<Integer>
            Set<Integer> hset = new TreeSet<Integer>();
 
            // Adding element to hset
            hset.add(20);
            hset.add(30);
            hset.add(40);
 
            // print the set
            System.out.println("Set: " + hset);
 
            // create typesafe view of the specified set
            Set<Integer>
                tsset = Collections
                            .checkedSet(hset, Integer.class);
 
            // printing the typesafe view of specified list
            System.out.println("Typesafe view of Set: " + tsset);
        }
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

Set: [20, 30, 40]
Typesafe view of Set: [20, 30, 40]