java 基本类型
· One min read
背景
了解java的基本类型,基本类型的大小和取值范围
platform:amd64
源码分析
在c++ standard 里面
| 类型 | 是否有符号 | 最小范围字节数 | type |
|---|---|---|---|
| char | implement defined [Type char is a distinct type that has an implementation-defined choice of “signed char” or “unsigned char” as its underlying type] | -- | |
| signed char | signed | -- | signed type |
| short int | signed | -- | signed type |
| int | signed | -- | signed type |
| long int | signed | -- | signed type |
| long long int | signed | -- | signed type |
在linux 64位下面
| java基本类型 | c/c++宏 |
|---|---|
| jint | int |
| jlong | long |
| jbyte | signed char |
| jboolean | unsigned char |
| jchar | unsigned short |
| jfloat | float |
| jdouble | double |
| jsize | jint 也就是int |
// jdk/src/java.base/unix/native/include/jni_md.h
typedef int jint;
#ifdef _LP64
typedef long jlong;
#else
typedef long long jlong;
#endif
typedef signed char jbyte;
// jdk/src/java.base/share/native/include/jni.h
#ifndef JNI_TYPES_ALREADY_DEFINED_IN_JNI_MD_H
typedef unsigned char jboolean;
typedef unsigned short jchar;
typedef short jshort;
typedef float jfloat;
typedef double jdouble;
typedef jint jsize;