java/ch/wlkl/javaExamples/ExGeneric.java

package ch.wlkl.javaExamples;

import static ch.wlkl.wsh.Top.sTrc;
import static ch.wlkl.env.Env.implement;
import java.io.FileInputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import static ch.wlkl.wsh.Top.sTrc;
import java.util.Arrays;

/**
 * 
 * @author walter
 */
public class  ExGeneric <T, U> extends ClassLoader {
    T myT = null; 
    U myU = null;
    /** Creates a new instance of ExGenericf */
    public ExGeneric(T my, U  yo) {
        myT = my;
        myU = yo;
    }
    
    public String toString () {
        return "exGeneric(" + asString(myT) + ", " + asString(myU) + ")";
    }
    public static String asString(Object o) {
    return o == null ? "NULL:null" : o.getClass().getName() + ":" + o;
    }

    public static <X, Y> ExGeneric<X, Y> pair (X x, Y y) {
        return new ExGeneric<X, Y> (x, y);
    }

    public static <X, Y> ExGeneric<Y, X> swap(ExGeneric<X, Y> o) {
        return new ExGeneric<Y, X> (o.myU, o.myT);
    }
     
    public void crack(ExGeneric<String, Integer> par) {
    System.out.println("crack(" + par +")");
    };   
    public <X extends C, Y extends C> void crackC(ExGeneric<X,Y> par) {
    System.out.println("crack(" + par +")");
    };   
    public static <X> ExGeneric<X, X> dupl(X x) {
    return pair(x, x);
    }
    public void run()
    {
        System.out.println("valueOf " + asString(null));
        System.out.println("valueOf " + asString(123));
        System.out.println("null =  " + null);
        System.out.println("start ExGeneric");
        System.out.println(new ExGeneric <Double, String> (1234., "abcd"));
        System.out.println(new ExGeneric <String, ExGeneric <Integer, Integer>> 
            ("zwei", new ExGeneric <Integer, Integer> (56, 78)));
        System.out.println(pair(pair(12, "zw�lf"), pair("zwei", pair("dreiDreiDrei", pair(3,33)))));
        System.out.println(swap(pair(1, "zwei")));
        System.out.println(swap(dupl(null)));
        // crack(dupl(null)); => syntax cannot apply
        System.out.println(swap(dupl(new C("@0"))));
      crackC(dupl(new CD("@CD")));
      // crack(dupl(new CD("CDeins"))); ==> syntax cannot find symbol....
    }
    
    public static <T> void pollution(Class<T> c, ArrayList<T> l) {
        for (T o: l)
            System.out.println("pollution<" + c + " l: " + o.getClass().toString() + " -> " + o);       
    }
    
    public static void pollution() {
        ArrayList<String> sl = new ArrayList<String>();
        sl.add("eins");
        sl.add("zwei");
        ArrayList<?> el = (ArrayList<?>) sl;
        ArrayList<Integer> il = (ArrayList<Integer>) el;
        il.add(new Integer(123));
        for (Object o: il)
            System.out.println("ele of il: " + o.getClass().toString() + " -> " + o);  
        pollution(String.class, sl);
        pollution(Integer.class, il);
        for (String o: sl)
            System.out.println("ele of sl: " + o.getClass().toString() + " -> " + o);       
    }
    
    public static <R> R receiverCast(Object o) {
        return (R) o;
    }

    public static void receiverCast() {
        String s = receiverCast(null);
        System.out.println("receveiverCast String - null " + s);
        s = receiverCast("string");
        System.out.println("receveiverCast String - string " + s);
        s = receiverCast(123);
        System.out.println("receveiverCast String - 123 " + s);
  }
    
    public static void arrayCast() {
//        String [] s0 = {};
//        System.out.println("s0");       
//        Object [] o0 = (Object[] ) s0;
//        System.out.println("o0");       
//        Integer [] i0 = (Integer[] ) o0;
           System.out.println("o0");       
        String [] sa = {"eins", "zwei"};
        System.out.println("sa[0] = " + sa[0] + ' ' + sa[0].getClass() +", sa[1] = " + sa[1] + ' ' + sa[01].getClass());       
        Object [] oa = (Object[] ) sa;
        System.out.println("oa[0] = " + oa[0] + ' ' + oa[0].getClass() +", oa[1] = " + oa[1] + ' ' + oa[01].getClass());       
        Integer [] ia = (Integer[] ) oa;
        System.out.println("ia[0] = " + ia[0] + ' ' + ia[0].getClass() +", ia[1] = " + ia[1] + ' ' + ia[01].getClass());       
        Number[] na = new Number[2];
        oa = na;
        ia = (Integer[]) na;
       
    }
 
    public static <T> T[] toArray(T... eles) {
        return eles;
    }
    public void compile() throws Exception {
        String name = "eins";
        String path = "E:\\java\\src\\" + name;
        String [] args = {path + ".java"};
                implement("java compiler" /*
        int res = com.sun.tools.javac.Main.compile(args, new java.io.PrintWriter(System.out));
        sTrc("compile rc " + res); */ );
        FileInputStream f = new FileInputStream(path + ".class");
        int len = f.available();
        sTrc(path + " avaiable " + len);
        byte[] byteCode = new byte[len+123];
        sTrc("read " + f.read(byteCode) + " available after " + f.available());
        f.close();
        Class<? extends Object> cl = defineClass(name, byteCode, 0, len);
        sTrc("defined class " + cl);
        Object o = cl.newInstance();
        sTrc("create object " + o);
        Method m = cl.getMethod("say");
        sTrc("found method " + m);
        m.invoke(o);
        m = cl.getMethod("sayStatic");
        sTrc("found method " + m);
        m.invoke(null);
    }

   
    public static void main(String [] arg)
    {
        Object[] a;
        System.out.println("toArray(a, b) = " + (a = toArray("a", "b")).getClass() + ' ' + Arrays.deepToString(a));
        System.out.println("toArray(1, 2) = " + (a = toArray(1, 2)).getClass() + ' ' + Arrays.deepToString(a));
        System.out.println("toArray(1, 2., dr) = " + (a = toArray(1, 2., "dr")).getClass() + ' ' + Arrays.deepToString(a));
        System.out.println("toArray(1, 2., dr, null) = " + (a = toArray(1, 2., "dr", null)).getClass() + ' ' + Arrays.deepToString(a));
        arrayCast();
        receiverCast();
        pollution();
    pair(0, '0').run();
    }
   
   class C {
    public C(String v) {
       val = v;
    }
    public String toString () {
        return val;
    }
    String val;
   }
   class CD extends C {
       public CD(String v) {
        super(v);
       }
   }
   class CE extends C {
       public CE(String v) {
        super(v);
       }
   }
 
}