java 泛型方法返回泛型结果_java返回泛型的方法-优快云博客

本文介绍了一个Java程序示例，展示了如何从HashMap中根据键获取不同类型的数据，并进行相应的类型转换。通过泛型方法实现了针对不同类型的处理逻辑，提高了代码的复用性和灵活性。

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https://blog.youkuaiyun.com/dekiven1/article/details/53928739

package testDouble;

import java.util.HashMap;

public class Test {
   static HashMap<String, String> sMap = new HashMap<String, String>();
   public static void main(String[] args) {

       sMap.put("1", "23");
       sMap.put("2", "ad");
       sMap.put("3", "1.0");
       sMap.put("4", "false");
       int i = getUserInfoByKey("1", Integer.class, 1);
       String s = getUserInfoByKey("2", String.class, "null");
       float f = getUserInfoByKey("3", Float.class, -0.1f);
       boolean b = getUserInfoByKey("4", Boolean.class, true);
       System.out.println("i:"+i);
       System.out.println("s:"+s);
       System.out.println("f:"+f);
       System.out.println("b:"+b);
   }

   protected static <T> T getUserInfoByKey(String key, Class<T> clazz, T deffault) {
       T ret = null;
       String v = sMap.get(key);
       if (deffault instanceof Integer) {
           ret = (clazz.cast(Integer.parseInt(v)));
       } else if (deffault instanceof String) {
           ret = clazz.cast(v);
       } else if (deffault instanceof Double) {
           ret = clazz.cast(Double.parseDouble(v));
       } else if (deffault instanceof Float) {
           ret = clazz.cast(Float.parseFloat(v));
       } else if (deffault instanceof Long) {
           ret = clazz.cast(Long.parseLong(v));
       } else if (deffault instanceof Boolean) {
           ret = clazz.cast(Boolean.parseBoolean(v));
       }
       if (null != ret) {
           return ret;
       }
       return deffault;
   }
}