Understanding Subtype in 5 Minutes

Transcript

1. ̑෼ͰΘ͔Δ෦෼ܕ ΤϜεϦʔ
   ߴౡ྄༞ʢ@rst76ʣ

2. ͳͥʁ

3. ෦෼ܕͱ͸ w ܕͷ্Լʢแؚʣؔ܎
   
   ෦෼ܕؔ܎
   w ԼҐͷܕΛ෦෼ܕͱݺͿ
   w +BWB
   ͷ৔߹ɺܧঝͰ࣮ݱ
   w ܕͷมԽʹͱ΋ͳ͏෦෼ܕؔ܎ͷมԽ
 ෆมɾڞมɾ൓ม

   Object Number Integer ্Ґͷܕ
   ਌ ԼҐͷܕ
   ࢠ

4. ෦෼ܕؔ܎̍ w ্Ґͷܕ͕ظ଴͞Ε͍ͯΔͱ͜ΖʹɺԼҐͷܕΛ࢖͏͜ͱ͸Ͱ͖Δ Function<Object, String> objFunc = o -> o.toString()

   + "!!!"; objFunc.apply(76); // => "76!!!" objFunc.apply("ten"); // => "ten!!!"

5. ෦෼ܕؔ܎̎ w ԼҐͷܕ͕ظ଴͞Ε͍ͯΔͱ͜Ζʹɺ্ҐͷܕΛ࢖͏͜ͱ͸Ͱ͖ͳ͍ Function<Integer, String> intFunc = i -> Integer.toString(i

   / 2) + "???"; intFunc.apply(76); // => "39???" intFunc.apply(new Object()); // => Compile Error

6. ؔ਺ͷ৔߹̍ w ؔ਺΋ܕ Function<Function<Number, String>, String> numFuncFunc = f ->

   f.apply(76.0); Function<Number, String> numFunc = n -> Integer.toString(n.intValue() / 4) + "..."; numFuncFunc.apply(numFunc); // => "19..."

7. ؔ਺ͷ৔߹̎ w Ҿ਺Ͱ౉ؔ͢਺ͷҾ਺͸ɺԼҐͷܕʹͰ͖ͳ͍ʂ
 ౉ؔ͢਺͸ɺҾ਺ͷܕʹ࿙Εͳ͘ରԠͰ͖Δʢ૝ఆ֎Ͱͳ͍ʣඞཁ͕͋Δ Function<Function<Number, String>, String> numFuncFunc = f

   -> f.apply(76.0); Function<Integer, String> intFunc = i -> Integer.toString(i * 2) + "???"; numFuncFunc.apply(intFunc); // => CompileError

8. ؔ਺ͷ৔߹̏ w ٯʹ্ҐͷܕΛҾ਺ʹͱΔؔ਺ͳΒɾɾɾ Function<Function<? super Number, String>, String> numFuncFunc =

   f -> f.apply(76.0); Function<Object, String> objFunc = o -> o.toString() + "!!!"; numFuncFunc.apply(objFunc); // => "76.0!!!"

9. ·ͱΊ w ܕͷ্Լؔ܎͸ɺؔ਺ͷҾ਺Ͱٯస͢Δ
   ˠ
   ൓ม
   w ܕ͸ָ͍͠ʂ
   w ؔ਺͸ָ͍͠ʂʂ

10. એ఻ w ʰϫϯεɾΞϙϯɾΞϯɾΞϧΰϦζϜʱ
 ɹͱ͍͏ຊΛ຋༁͠·ͨ͠
    w ༗໊ͳөըΛ୊ࡐʹɺܭࢉػՊֶΛղઆ͍ͯ͠·͢