Copying Arrays of Data Between PeopleCode and Java
When PeopleCode is called from your Java program it executes what are called native methods. These methods looks like regular Java methods in their definition but are implemented in the PeopleTools layer. In order to go from Java into PeopleTools you have to use an interface called the Java Native Interface (JNI). There is a cost associated with each transition across the JNI. Using the CopyToJavaArray and the CopyFromJavaArray functions may improve your performance, as they act as a type of bulk data copy that minimizes the transition overhead.
For example you could copy an array by copying each element using the array's Get method. However, that would require traversing the JNI twice for each element; once going into Tools and once coming back from Tools. Not only is there transition overhead but there is also conversion between object types. For example a PeopleCode string has to be converted to a Java String and vice-versa. While these two builtins do not eliminate the latter conversions, they minimize the number of transitions across the JNI.
These functions can be used when you are selecting data into a PeopleCode array and you want to copy that data into a Java array.
These functions also allow you to supply an optional parameter that specifies the list of items you want copied.