表达式的类型转换

矫情吗；* 2024-02-17 17:47 35阅读 0赞

一段小程序来解释表达式中的各个数据类型的转换机制。

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：

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。