Java八种基本数据类型占用字节数空间介绍

大家都知道在java中有八种基本数据类型,他们所占得空间当然也是不一样的。所占空间如下:

byte:1字节

short:2字节

int:4字节

long:8字节

char:2字节

float:4字节

double:8字节

boolean:不确定

本来boolean应该只占用1bit也就是1/8字节的,但实际上,由于Java的实际寻址单元最小是byte即1字节,所以所以实际上boolean占用的是可能是1bit,也可能是更多,这个是不确定的。下面是Sun的官方介绍。

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.

再下面是jvm虚拟机规范的介绍(JVM规范第2版 3.3.4节):

Where Java programming language boolean values are mapped by compilers to values of Java virtual machine type int, the compilers must use the same encoding.

所以只是单纯的boolean b = true;这里的b占用4个字节,和int一样。

而紧接着下面还有一段:

Arrays of type boolean are accessed and modified using the byte array instructions
In Sun's JDK releases 1.0 and 1.1, and the Java 2 SDK, Standard Edition, v1.2, boolean arrays in the Java programming language are encoded as Java virtual machine byte arrays, using 8 bits per boolean element.

所以说boolean[] b = new boolean[10];这样的数组中每个值占用的空间是1字节。

 

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