Editing Java Native Interface (section)

== Mapping types ==
The following table shows the mapping of types between Java (JNI) and native code.

{| class="wikitable"
!C Type
!Java Language Type
!Description
!Type signature
|-
| {{mono|unsigned char<br/>uint8_t}}
| {{mono|jboolean}}
|unsigned 8 bits
| {{mono|Z}}
|-
| {{mono|signed char<br/>int8_t}}
| {{mono|jbyte}}
|signed 8 bits
| {{mono|B}}
|-
| {{mono|unsigned short<br/>uint16_t}}
| {{mono|jchar}}
|unsigned 16 bits
| {{mono|C}}
|-
| {{mono|short<br/>int16_t}}
| {{mono|jshort}}
|signed 16 bits
| {{mono|S}}
|-
| {{mono|int<br/>int32_t}}
| {{mono|jint}}
|signed 32 bits
| {{mono|I}}
|-
| {{mono|long long<br/>int64_t}}
| {{mono|jlong}}
|signed 64 bits
| {{mono|J}}
|-
| {{mono|float}}
| {{mono|jfloat}}
|32 bits
| {{mono|F}}
|-
| {{mono|double}}
| {{mono|jdouble}}
|64 bits
| {{mono|D}}
|-
| {{mono|void}}
|
|
| {{mono|V}}
|}

In addition, the signature <code>"L {{Sic|hide=y|fully|-}}qualified-class ;"</code> would mean the class uniquely specified by that name; e.g., the signature <code>"Ljava/lang/String;"</code> refers to the class {{Javadoc:SE|package=java.lang|java/lang|String}}. Also, prefixing <code>[</code> to the signature makes the array of that type; for example, <code>[I</code> means the int array type (<code>int[]</code>). Finally, a <code>void</code> signature uses the <code>V</code> code.

These types are interchangeable. One can use <code>jint</code> where you normally use an <code>int</code>, and vice versa, without any [[type conversion|typecast]]ing required. However, mapping between Java Strings and arrays to native strings and arrays is different. If a <code>jstring</code> is used where a <code>char *</code> would be, the code could crash the JVM.{{original research inline|date=February 2017}}