JNI GetFieldID and GetMethodID required signature parameters

When calling JNI's GetMethodID function to obtain a jmethodID, you need to pass in a method name and method signature. The method name is the method name defined in Java. The format of the method signature is: (parameter parameter type list) return value.

1. Basic type signature

Java	Native	Signature
byte	jbyte	B
char	jchar	C
double	jdouble	D
float	jfloat	F
int	jint	I
short	jshort	S
long	jlong	J
boolean	jboolean	Z
void	void	V

2. Conversion of reference data type.

Java	Native	Signature
All objects	jobject	L+classname +;
Class	jclass	Ljava/lang/Class;
String	jstring	Ljava/lang/String;
Throwable	jthrowable	Ljava/lang/Throwable;
Object[]	jobjectArray	[L+classname +;
byte[]	jbyteArray	[B
char[]	jcharArray	[C
double[]	jdoubleArray	[D
float[]	jfloatArray	[F
int[]	jintArray	[I
short[]	jshortArrsy	[S
long[]	jlongArray	[J
boolean[]	jbooleanArray	[Z

Get signature method:

1. Spelling yourself
For example:

Method: int (int param);

Signature: (I)I

Second, the command line generation

1. Use javac to generate a class file corresponding to the java file;

2. Use the javap -s -p command to obtain the corresponding signature information, as shown in the figure:

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