CallableStatements and INOUT Parameters

INOUT parameters map to an array of the parameter type in Java. (The method must take an array as its parameter.) This conforms to the recommendations of the SQL standard.

Given the following example:
CallableStatement call = conn.prepareCall(
    "{CALL doubleMyInt(?)}");
// for inout parameters, it is good practice to
// register the outparameter before setting the input value
call.registerOutParameter(1, Types.INTEGER);
int retval = call.getInt(1);
The method doubleIt should take a one-dimensional array of ints. Here is sample source code for that method:
public static void doubleMyInt(int[] i) {
    i[0] *=2;
    /* Derby  returns the first element of the array.*/
Note: The return value is not wrapped in an array even though the parameter to the method is.
Table 1. INOUT Parameter Type Correspondence
JDBC Type Array Type for Method Parameter Value and Return Type
BIGINT long[] long
BINARY byte[][] byte[]
BIT boolean[] boolean
DATE java.sql.Date[] java.sql.Date
DOUBLE double[] double
FLOAT double[] double
INTEGER int[] int
LONGVARBINARY byte[][] byte[]
REAL float[] float
SMALLINT short[] short
TIME java.sql.Time[] java.sql.Time
TIMESTAMP java.sql.Timestamp[] java.sql.Timestamp
VARBINARY byte[][] byte[]
OTHER yourType[] yourType
JAVA_OBJECT (only valid in Java2/JDBC 2.0 environments) yourType[] yourType

Register the output type of the parameter before executing the call. For INOUT parameters, it is good practice to register the output parameter before setting its input value.

Related reference
CallableStatements and OUT Parameters