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package com.Test;
import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;
public class M {
public static void main(String[] args){
testMap();
}
private static void testMap(){
Map<String,String> mapStr=new HashMap<String, String>();
Map<String,Object> mapObj=new HashMap<String, Object>();
mapObj.put("key1",new BigDecimal(1));
mapStr=(Map)mapObj;//为什么允许这样的类型转换?
String s=mapStr.get("key1");//Exception in thread "main" java.lang.ClassCastException: java.math.BigDecimal cannot be cast to java.lang.String
}
}