xyang

1.?自動(dòng)裝箱與拆箱?對(duì)應(yīng)C#
?例1.1
??Integer?i?=?10;
??int?j?=?i;
??
2.?更優(yōu)化的for循環(huán)?對(duì)應(yīng)就C#---foreach循環(huán)
?例2.1
??String[]?names?=?{"BadBoy","GoodBoy","HappyGirl","sadGirl"};
??for(String?option:?names)?{
???System.out.println(option);
??}
?例2.2?加泛型?對(duì)應(yīng)C++模板
??import?java.util.*;
??
??ArrayList<String>?animals?=?new?ArrayList<String>();
??animals.add("Dog");
??animals.add("Cat");
??animals.add("Chick");
??animals.add("Cow");
??for(String?option?:?animals)?{
???System.out.println(option);
??}
??
3.參數(shù)可變的方法和printf
?例3.1
??定義:
??public?int?sum(int...?n)?{??//傳過(guò)來(lái)n為一個(gè)int型數(shù)組
???int?tempSum;
???for(int?option?:?n)?{
????tempSum+=option;
???}
???/*
???for(int?i?=?0;?i?<?n.length;?i++)?{
????tempSum+=n[i];
???}
???*/
???return?tempSum;
??}
??調(diào)用1:?sum(1);
??調(diào)用2:?sum(1,2);
??調(diào)用3:?sum(1,2,3,4);
?例3.2?printf方法,??對(duì)應(yīng)c語(yǔ)言的printf
??int?x?=?10;
??int?y?=?20;
??int?sum?=?x?+?y;
??System.out.printf("%d?+?%d?=?%d",x,y,sum);
4.?枚舉
?例4.1
??public?enum?MyColors?{
???red,
???black,
???blue,
???green,
???yellow
??}
??
??MyColors?color?=?MyColors.red;
??for(MyColors?option?:?color.values())?{
???System.out.println(option);
??}

/**不能在switch語(yǔ)句里這樣寫case?MyColors.red:
?*這樣編譯器不會(huì)讓你通過(guò)*/
switch(color)?{
?case?red:
??System.out.println("best?color?is?"+red);
??break;
?case?black:
??System.out.println("NO?"?+?black);
??break;
?default:
??System.out.println("What");
??break;
}

5.靜態(tài)引用
?例5.1
??1.5版本以前的寫法是：
?
??　　import?java.lang.Math;?//程序開(kāi)頭處
??
??　　...
??
??　　double?x?=?Math.random();?
??1.5版本中可以這樣寫
???import?static?java.lang.Math.random;?//程序開(kāi)頭處
???
???...
??　　
???double?x?=?random();??