爪哇 - 從字符串轉換爲通用類型

在C＃中，我可以做這樣的事情爪哇 - 從字符串轉換爲通用類型

public static TConvertible ChangeType<TConvertible>(object value) where TConvertible : IConvertible 
    { 
     try 
     { 
      if (value == null) 
       return default(TConvertible); 

      return (TConvertible)Convert.ChangeType(value, typeof(TConvertible)); 
     } 
     catch (System.FormatException) 
     { 
      return default(TConvertible); 
     } 
    }

有沒有辦法做到在Java類似的東西？我正在使用android SharedPreferences並嘗試圍繞它包裝管理類。我不想使用getString，getInt,getLong等，我想傳遞值，將它作爲一個字符串存儲，然後將其轉換回來。

來源

2011-02-18 Josh

你能給你想什麼方法調用（一個或多個），以使看起來像一個例子嗎？ – TofuBeer 2011-02-18 16:43:45

我相信這是不可能的，因爲Java的泛型實現和整個類型的擦除問題，因爲它不知道TConvertible是在運行時。

來源

2011-02-18 16:27:53

我很害怕這是答案。 – Josh 2011-02-18 16:59:51

試試我的新類

/* 
* To change this template, choose Tools | Templates 
* and open the template in the editor. 
*/ 
package sk.freeit.utils; 

import java.lang.reflect.Constructor; 
import java.lang.reflect.InvocationTargetException; 
import java.lang.reflect.Method; 

/** 
* 
* @author radenko 
* [email protected] 
*/ 
public class Convert { 
    protected static Object invokeMethod(Object obj, String valMethod) throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException { 
     Method intValue = obj.getClass().getMethod(valMethod); 
     return intValue.invoke(obj); 
    } 

    protected static Object makeNew(Class type, Object obj) throws NoSuchMethodException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException { 
     Constructor constructor = type.getConstructor(obj.getClass()); 
     return constructor.newInstance(obj); 
    } 

    public static boolean booleanValue(String str) { 
     str = str.toLowerCase(); 
     return !str.isEmpty() && !str.equals("0") && !str.equals("no") && !str.equals("n") && !str.equals("false"); 
    } 

    public static boolean booleanValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return (Boolean)obj; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj)!=0; 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return ((Character)obj)!='\0'; 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj)!=0.0; 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj)!=0.0; 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj)!=0.0; 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj)!=0L; 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj)!=0; 
     else if(srcType.equals(String.class)) 
      return booleanValue(obj.toString());   
     else { 
      try { 
       return (Boolean)invokeMethod(obj, "booleanValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     } 

     return booleanValue(obj.toString()); 
    } 

    public static byte byteValue(Object obj) { 
     Class srcType = obj.getClass(); 
     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?(byte)1:(byte)0; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return (byte)Character.getNumericValue((Character)obj); 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).byteValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj).byteValue(); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj).byteValue(); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj).byteValue(); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj).byteValue(); 
     else if(srcType.equals(String.class)) 
      return Byte.parseByte((String)obj); 
     else { 
      try { 
       return (Byte)invokeMethod(obj,"byteValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     }   

     return Byte.parseByte(obj.toString()); 
    } 

    public static char charValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?'\0':'Y'; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return Character.forDigit((Byte)obj,10); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return (Character)obj; 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return Character.forDigit(((Double)obj).intValue(),10); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return Character.forDigit(((Float)obj).intValue(),10); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return Character.forDigit((Integer)obj,10); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return Character.forDigit(((Long)obj).intValue(),10); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return Character.forDigit((Short)obj,10); 
     else if(srcType.equals(String.class)) 
      return ((String)obj).charAt(0); 
     else { 
      try { 
       return (Character)invokeMethod(obj, "charValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     }   

     return obj.toString().charAt(0); 
    } 

    public static double doubleValue(Object obj) { 
     Class srcType = obj.getClass(); 
     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?1.0:0.0; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj).doubleValue(); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return Character.getNumericValue((Character)obj); 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).doubleValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj).doubleValue(); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj).doubleValue(); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj).doubleValue(); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj).doubleValue(); 
     else if(srcType.equals(String.class)) 
      return Double.parseDouble((String)obj); 
     else { 
      try { 
       return (Double)invokeMethod(obj, "doubleValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     }  

     return Double.parseDouble(obj.toString()); 
    } 

    public static float floatValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?1.0f:0.0f; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return Character.getNumericValue((Character)obj); 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).floatValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj).floatValue(); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj); 
     else if(srcType.equals(String.class)) 
      return Float.parseFloat((String)obj); 
     else { 
      try { 
       return (Float)invokeMethod(obj, "floatValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     } 

     return Float.parseFloat(obj.toString()); 
    } 

    public static int intValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?1:0; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj).intValue(); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) { 
      return Character.getNumericValue((Character)obj); 
     } 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).intValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj).intValue(); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj).intValue(); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj).intValue(); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj).intValue(); 
     else if(srcType.equals(String.class)) 
      return Integer.parseInt((String)obj); 
     else { 
      try { 
       return (Integer)invokeMethod(obj, "intValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     }  

     return Integer.parseInt(obj.toString()); 
    } 

    public static long longValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?1:0; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return Character.getNumericValue((Character)obj); 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).longValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj).longValue(); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj); 
     else if(srcType.equals(String.class)) 
      return Long.parseLong((String)obj); 
     else { 
      try { 
       return (Long)invokeMethod(obj, "longValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     }  

     return Long.parseLong(obj.toString()); 
    } 

    public static short shortValue(Object obj) { 
     Class srcType = obj.getClass(); 

     if (srcType.equals(boolean.class)||srcType.equals(Boolean.class)) 
      return ((Boolean)obj)?(short)1:(short)0; 
     else if (srcType.equals(byte.class) || srcType.equals(Byte.class)) 
      return ((Byte)obj).shortValue(); 
     else if (srcType.equals(char.class) || srcType.equals(Character.class)) 
      return (short)Character.getNumericValue((Character)obj); 
     else if (srcType.equals(double.class) || srcType.equals(Double.class)) 
      return ((Double)obj).shortValue(); 
     else if (srcType.equals(float.class) || srcType.equals(Float.class)) 
      return ((Float)obj).shortValue(); 
     else if (srcType.equals(int.class) || srcType.equals(Integer.class)) 
      return ((Integer)obj).shortValue(); 
     else if (srcType.equals(long.class) || srcType.equals(Long.class)) 
      return ((Long)obj).shortValue(); 
     else if (srcType.equals(short.class) || srcType.equals(Short.class)) 
      return ((Short)obj); 
     else if(srcType.equals(String.class)) 
      return Short.parseShort((String)obj); 
     else { 
      try { 
       return (Short)invokeMethod(obj, "shortValue"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
     } 

     return Short.parseShort(obj.toString()); 
    }  

    public static Object changeType (Object obj, Class type) { 
     if (obj.getClass().equals(type)) return obj; 

     if (type.equals(boolean.class)||type.equals(Boolean.class)) 
      return booleanValue(obj); 
     else if (type.equals(byte.class) || type.equals(Byte.class)) 
      return byteValue(obj); 
     else if (type.equals(char.class) || type.equals(Character.class)) 
      return charValue(obj); 
     else if (type.equals(double.class) || type.equals(Double.class)) 
      return doubleValue(obj); 
     else if (type.equals(float.class) || type.equals(Float.class)) 
      return floatValue(obj); 
     else if (type.equals(int.class) || type.equals(Integer.class)) 
      return intValue(obj); 
     else if (type.equals(long.class) || type.equals(Long.class)) 
      return longValue(obj); 
     else if (type.equals(short.class) || type.equals(Short.class)) 
      return shortValue(obj); 
     else if(type.equals(String.class)) 
      return obj.toString(); 
     else { 
      try { 
       invokeMethod(obj,type.getName()+"Value"); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 

      try { 
       invokeMethod(obj,"to"+type.getName()); 
      } catch (NoSuchMethodException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      } 
      try { 
       return makeNew(type, obj); 
      } catch (NoSuchMethodException ex) { 
      } catch (InstantiationException ex) { 
      } catch (IllegalAccessException ex) { 
      } catch (IllegalArgumentException ex) { 
      } catch (InvocationTargetException ex) { 
      }    
     }   

     return type.cast(obj); 
    } 
}

Radenko

來源

2013-05-23 21:18:31 Radenko

爪哇 - 從字符串轉換爲通用類型

回答

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