I'll go out on a limb here and say that .h files are for c \ c++, not to much to do with Java\Processing.  (unless I'm really missing something). How are you making your 'library'?

well I'm normal from making h files in C/ C++ but how do i then. Because also when i make a new library and with jar files it still can't find it getting stress of it.

this is example of a H file that i need

#ifndef String_h
#define String_h

#include "WProgram.h"
#include <string.h>
#include <ctype.h>

class String
{
  public:
    String(const int length = 16);
    String(const char* bytes);
    String(const String &str);

    const String & operator = ( const String &rightStr );
    const String & operator = ( const char*);

    const String & operator +=( const String &rightStr );
    const String & operator +=( const char );
    const String & operator +=( const char* bytes);
    const String & operator +=( long n );
    const String & operator +=( int n );
    //const operator boolean ==() as an alias to equals().

  
    const String & append(char);
    const String & append(char *str);
    const String & append(int n, int base);
    const String & append(long n, int base);
    const String & append(int n);
    const String & append(long n);
    const String & append(const String &str);

    //friend String operator +(const String &s1, char c2);
    //friend String operator +(const String &s1, const String &s2);
    //friend String operator +(const String &s1, const char *s2);
    //friend String operator +(const char *s1, const String &s2);
    //friend String operator +(char c1, const String &s2);
    //friend String operator +(const String &s1, int n);
    //friend String operator +(int n, const String &s1);
    //friend String operator +(const String &s1, long n);
    //friend String operator +(long n, const String &s1);

    char charAt(int index);
    void setCharAt(int index, char ch);

    //const String & concat(const String &str);

    boolean equals(char* str);
    boolean equals(const String &str);
    boolean contains(char* str);
    byte* getBytes();
    void setArray(const char* bytes);
    int indexOf(int ch);
    int indexOf(const String &str);
    int indexOf(char ch, int fromIndex);
    int indexOf(const String &str, int fromIndex);
    int length() {return _length;}
    int capacity() {return _capacity;}
    boolean startsWith(const String &prefix);
    boolean startsWith(const String &prefix, int offset);
    String substring(int beginIndex);
    String substring(int beginIndex, int endIndex);

    //static String valueOf(int n, int base);
    //static String valueOf(long n, int base);

    static char* valueOf(int n, int base);
    static char* valueOf(long n, int base);

    const char*    cstr() const { return _array; }
    operator char*() { return _array; }
 
    char* getChars();
    void trim(void);
    boolean endsWith(const String &suffix);
    void replace(char oldChar, char newChar);
    void toLowerCase();
    void toUpperCase();
    void clear(void);


    char *_array;       // the actual char array
    uint16_t _length;   // the string length
    uint16_t _capacity; // the array length

    String version(void);    // the version number

     ~String();            // destructor


  private:

};

#endif


because i have to make a lamp that goes on via the internet and have to do this via processing and not via
 an outher program. Until now i have it but want to make h file but cant load it into it :S.

http://wiki.processing.org/w/How_to_Install_a_Contributed_Library

I read those to, but I was trying that and it didnt work I always get the fault that it doesn't exist. So i don't know what I do wrong, when there was a movie about how to do it it would be much easier for me and outher people.

In Java, you have no headers, you define classes in regular .java files (or .pde in Processing, but you can use both there). Classes contain both the declarations and the implementation, which looks strange to people coming from the C++ world. You can use interfaces if you want to define pure APIs.

To be clear, it is not possible to use .h or .c files with Processing. We do not (and will never) support developing native Android code (i.e. the NDK) using the Processing development environment.