SortaMap<Key,Value>byvalues(Java)HashMap按value值排序

     对HashMap按value值的大小进行排序，方法如下。

import java.util.*;public class MapUtil{    public static > Map         sortByValue( Map map )    {        List> list =            new LinkedList>( map.entrySet() );        Collections.sort( list, new Comparator>()        {            public int compare( Map.Entry o1, Map.Entry o2 )            {                return (o1.getValue()).compareTo( o2.getValue() );            }        } );        Map result = new LinkedHashMap();        for (Map.Entry entry : list)        {            result.put( entry.getKey(), entry.getValue() );        }        return result;    }}

And an associated JUnit4 test so you don't have to take my word for it:

import java.util.*;
import org.junit.*;

public class MapUtilTest
{
    @Test
    public void testSortByValue()
    {
        Random random = new Random(System.currentTimeMillis());
        Map testMap = new HashMap(1000);
        for(int i = 0 ; i <1000 ; ++i) {
            testMap.put( "SomeString" + random.nextInt(), random.nextInt());
        }

        testMap = MapUtil.sortByValue( testMap );
        Assert.assertEquals( 1000, testMap.size() );

        Integer previous = null;
        for(Map.Entry entry : testMap.entrySet()) {
            Assert.assertNotNull( entry.getValue() );
            if (previous != null) {
                Assert.assertTrue( entry.getValue() >= previous );
            }
            previous = entry.getValue();
        }
    }

}

Java 7 Version:

public static > Map 
    sortByValue( Map map )
{
    List> list =
        new LinkedList<>( map.entrySet() );
    Collections.sort( list, new Comparator>()
    {
        @Override
        public int compare( Map.Entry o1, Map.Entry o2 )
        {
            return ( o1.getValue() ).compareTo( o2.getValue() );
        }
    } );

    Map result = new LinkedHashMap<>();
    for (Map.Entry entry : list)
    {
        result.put( entry.getKey(), entry.getValue() );
    }
    return result;
}

Java 8 Version:

public static > Map 
    sortByValue( Map map )
{
    Map result = new LinkedHashMap<>();
    Stream> st = map.entrySet().stream();

    st.sorted( Map.Entry.comparingByValue() )
        .forEachOrdered( e -> result.put(e.getKey(), e.getValue()) );

    return result;
}

在JAVA8版本中，

st.sorted(Map.Entry.comparingByValue()).forEachOrdered(e->result.put(e.getKey(), e.getValue()));

也可写成：

 st.sorted(Comparator.comparing(e -> e.getValue())).forEach(e -> result.put(e.getKey(), e.getValue()));

以上是按照升序排序的，按照降序排序方法如下：

import java.util.*;
import java.util.stream.Stream;

public class MapUtil {

public static > Map sortByValue( Map map) {
    Map result = new LinkedHashMap<>();
    Stream> st = map.entrySet().stream();
    
    Comparator ok = new Comparator>()
        {
            public int compare( Map.Entry o1, Map.Entry o2 )
            {
                return (o2.getValue()).compareTo( o1.getValue() );
            }
        };

    st.sorted(ok).forEachOrdered(e->result.put(e.getKey(), e.getValue()));
    return result;
}
}