Java基本类型转换的优先顺序

Java中经常碰到两个不同类型的基本类型数据进行运算，当没有强制类型转化时，它们之间总会有一个标准去衡量最终的计算结果是什么类型的吧，下面以一个简单的例子看看默认的优先顺序：

public class Main {
    public static void main(String[] args) {
        byte by = 2;
        short sh = 4;
        char ch = 'a';
        int in = 8;
        long lo = 9;
        float fl = 10.7f;
        double dou = 34.98;
        boolean boo = true;
        System.out.println("byte+byte: " + getType(by + by));
        System.out.println("short+short: " + getType(sh + sh));
        System.out.println("char+char: " + getType(ch + ch));
        System.out.println("byte+short: " + getType(by + sh));
        System.out.println("byte+char: " + getType(by + ch));
        System.out.println("short+char: " + getType(sh + ch));
        System.out.println("byte+int: " + getType(by + in));
        System.out.println("short+int: " + getType(sh + in));
        System.out.println("char+int: " + getType(ch + in));
        System.out.println("int+long: " + getType(in + lo));
        System.out.println("int+float: " + getType(in + fl));
        System.out.println("int+double: " + getType(in + dou));
        System.out.println("long+float: " + getType(lo + fl));
        System.out.println("float+double: " + getType(fl + dou));
        System.out.println("long+double: " + getType(lo + dou));
        System.out.println("boolean: " + getType(boo));
    }

    public static String getType(Object o) {
        return o.getClass().getSimpleName().toString();
    }
}

执行结果为：

byte+byte: Integer
short+short: Integer
char+char: Integer
byte+short: Integer
byte+char: Integer
short+char: Integer
byte+int: Integer
short+int: Integer
char+int: Integer
int+long: Long
int+float: Float
int+double: Double
long+float: Float
float+double: Double
long+double: Double
boolean: Boolean

很清楚啦，byte、short、char是一个级别的，它们之间的运算都会转换为int类型，注意，自己跟自己运算也会转为int类型。int之后从小到大依次为：long、float、double。至于boolean，他是个比较特殊的类型，官方文档也给的模棱两可：

boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined.

它的功能是一个bit能实现的，但是他的存储空间没有明确定义，更别提跟别的类型进行运算了。
一个表格总结Java基本类型的优先顺序：

Java基本类型转换的优先顺序

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