I think this issue needs a fix or walkaround.  Many open source api cannot be used because of this.  Equivalently, this issue is like one cannot pass 'o' as a marker in plot command in Octave.  I build a simple code to demonstrate the issue:

import java.lang.String;
import java.lang.Integer;
import java.lang.Double;
import java.lang.Character;

public final class test_char {

public test_char() {}

public static Integer case_string(String s) {
Integer ii = 1;
        return ii;
}
public static Double  case_char(Character s){
Double ii = 2.;
        return ii;
}
}
/**

I think this issue needs a fix or walkaround.  Many open source api cannot be used because this.  Equivalently, this issue is like one cannot pass 'o' as a marker in plot command.  I build a simple code to demonstrate this issue:

The observations are:
(1) 'o' and javaObject('java.lang.String', 'o') are both passed to this java code as string
(2) No solution to create a java character. 

>> javaMethod('case_string', 'test_char', javaObject('java.lang.String', 'o'))

ans = 1

>> javaMethod('case_string', 'test_char', 'o')

ans = 1

>> javaMethod('case_char', 'test_char', 'o')

error: [java] java.lang.NoSuchMethodException: case_char

>> javaObject('java.lang.Character', '1')

error: [java] java.lang.NoSuchMethodException: java.lang.Character

(file #52336, file #52337)