表达式的类型转换

一段小程序来解释表达式中的各个数据类型的转换机制。

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

package com.liaojianya.chapter1; /**  * This program demonstrates the convertion of data type.  * @author LIAO JIANYA  *  */ public class TypeConvert6_17 {     public static void main(String[] args)     {         char ch = 'a';         short a = -2;         int b = 3;         float f = 5.3f;         double d = 6.28;           System.out.println("ch / a = " + ch / a);         System.out.println("the type of (ch / a) is :  " + getType((ch / a)));                   System.out.println("d / f = " + d / f);         System.out.println("the type of (d / f) is :  " + getType((d / f)));                   System.out.println("a + b = " + (a + b));         System.out.println("the type of (a + b) is :  " + getType((a + b)));                   System.out.println("(ch / a) - (d / f) - (a + b) = " + ((ch / a) - (d / f) - (a + b)));             System.out.println("the type of ((ch / a) - (d / f) - (a + b)) is :  "         + getType(((ch / a) - (d / f) - (a + b))));     }         public static String getType(Object o)         {             return o.getClass().toString();         }         public static String getType(int o)         {             return "int";         }         public static String getType(char o)         {             return "char";         }         public static String getType(short o)         {             return "short";         }         public static String getType(float o)         {             return "short";         }         public static String getType(double o)         {             return "double";         }   }

　　运行结果：

?

1 2 3 4 5 6 7 8

ch / a = -48 the type of (ch / a) is :  int d / f = 1.1849056177353188 the type of (d / f) is :  double a + b = 1 the type of (a + b) is :  int (ch / a) - (d / f) - (a + b) = -50.18490561773532 the type of ((ch / a) - (d / f) - (a + b)) is :  double

　分析：

　1）占用字节较少的数据类型转换成占用字节较多的数据类型。

　2）字符类型会转换成int类型。

　3）int类型会转换成float类型。

　4）表达式中出现double，则其他操作数也会转换成double类型。

　5）总结：大鱼吃小鱼：占字节多的替换占字节少的；精度高的优先；优先级排序：byte，short，int，long，float，double。