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Java Collections - Collections.checkedNavigableMap() Examples

Java Collections Java Java API 

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Class:

java.util.Collections

java.lang.Objectjava.lang.Objectjava.util.Collectionsjava.util.CollectionsLogicBig

Method:

public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K,V> m,
                                                          Class<K> keyType,
                                                          Class<V> valueType)

Returns a dynamically typesafe view of the specified NavigableMap.


Examples


Without CheckedNavigableMap 

package com.logicbig.example.collections;

import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;

public class CheckedNavigableMapExample {

    public static void main(String... args) {
        NavigableMap<Integer, String> map = new TreeMap<>();
        map.put(1, "one");
        System.out.println(map);

        Map map2 = map;
        map2.put(2, 1000);
        System.out.println(map2);
    }
}

Output

{1=one}
{1=one, 2=1000}




Using checkedNavigableMap 

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;

public class CheckedNavigableMapExample2 {

    public static void main(String... args) {
        NavigableMap<Integer, String> map = new TreeMap<>();
        map = Collections.checkedNavigableMap(map, Integer.class, String.class);
        map.put(1, "one");
        System.out.println(map);

        Map map2 = map;
        map2.put(2, 1000);
        System.out.println(map2);
    }
}

Output

Caused by: 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.logicbig.example.collections.CheckedNavigableMapExample2.main(CheckedNavigableMapExample2.java:23)
	... 6 more

See Also