Java Collections checkedSortedMap()

checkedSortedMap() 用于获取指定SortedMap的动态类型安全视图。

1 语法

public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K,V> m, Class<K> keyType, Class<V> valueType)

2 参数

m：返回动态类型安全视图的映射。

keyType：允许Map的key的类型。

valueType：允许Map的value的类型。

3 返回值

返回指定SortedMap的动态类型安全视图。

4 Collections checkedSortedMap()示例1

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.checkedSortedMap的例子
 */
import java.util.*;

public class Demo {

    public static void main(String[] args) {
        //create map
        SortedMap<String, Integer> smap = new TreeMap<String, Integer>();
        //Insert values in the Map
        smap.put("yiidian", 1100);
        smap.put("baidu", 500);
        smap.put("google", 1300);
        smap.put("ABCD", 1200);
        //Get type safe view of the sorted Map
        System.out.println("Type safe view of the Sorted Map is: "+Collections.checkedSortedMap(smap,String.class,Integer.class));
    }
}

输出结果为：

Type safe view of the Sorted Map is: {ABCD=1200, baidu=500, google=1300, yiidian=1100}

5 Collections checkedSortedMap()示例2

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.checkedSortedMap的例子
 */
import java.util.*;

public class Demo {

    public static void main(String[] args) {
        //create map
        SortedMap<Integer, String> smap = new TreeMap<Integer, String>();
        //Insert values in the Map
        smap.put(1100, "yiidian");
        smap.put(500, "baidu");
        smap.put(1800, "google");
        smap.put(900, "ABCD");
        //Get type safe view of the sorted Map
        System.out.println("Type safe view of the Sorted Map is: "+Collections.checkedSortedMap(smap,Integer.class,String.class));
    }
}

输出结果为：

Type safe view of the Sorted Map is: {500=baidu, 900=ABCD, 1100=yiidian, 1800=google}

6 Collections checkedSortedMap()示例3

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.checkedSortedMap的例子
 */
import java.util.*;

public class Demo {

    public static void main(String[] args) {
        //create map
        SortedMap<Integer, String> map = new TreeMap<>();
        map = Collections.checkedSortedMap(map,Integer.class, String.class);
        map.put(1100, "yiidian");
        map.put(500, "baidu");
        map.put(1800, "google");
        map.put(900, "ABCD");
        //Get type safe view of sorted map
        System.out.println("Map content: "+map);
        SortedMap map2 = map;
        map2.put(5,500);
        map2.put(6,200); //throws ClassCastException
    }
}

输出结果为：

Map content: {500=baidu, 900=ABCD, 1100=yiidian, 1800=google}
Exception in thread "main" java.lang.ClassCastException: Attempt to insert class java.lang.Integer value into map with value type class java.lang.String
	at java.util.Collections$CheckedMap.typeCheck(Collections.java:3577)
	at java.util.Collections$CheckedMap.put(Collections.java:3620)
	at com.yiidian.Demo.main(Demo.java:24)