Hadoop的Mapper和Reducer如何共享变量

public class ShortestPath {
 static Map<String, Integer> map=new HashMap<String, Integer>();

 public static class TokenizerMapper extends Mapper<LongWritable, Text, Text, Text> {
   public void map(LongWritable key, Text value, Context context)
                throws IOException, InterruptedException {
         map.put("test",123");
   }
 }
    
 public static class ShortestPathReducer extends Reducer<Text, Text, Text, Text> {
   public void reduce(Text key, Iterable<Text> values, Context context)
                throws IOException, InterruptedException {
        map.put("test",123");
  }
 }

 public static void main(String[] args) throws Exception {
  　　System.out.println(map.toString()); 
 }
}

虽然编译成功，但在main中的输出显示，map为null。

求教如何使mapper和reducer能共享变量？