Java中替代C# ref/out 关键字方案:

刚学习Java不久，今天遇到一个问题，需要在方法中修改传入的对象的值，确切的说是需要使用一个方法，创建一个对象，并把其引用返回，熟悉C#的我
的第一反应就是C#中的ref/out关键字,结果发现Java中没有类似的关键字，所以只能想想如何解决此问题.

参数传递:
方法的参数传递有两种，一种是值传递，一种是引用传递,但是其实都是拷贝传递。

值传递：就是把传递的【数据本身拷贝一份】，传入方法中对其进行操作，拷贝的是值。
引用传递：就是把指向某个对象的【引用拷贝一份】，传入方法中通过此引用可以对对象进行操作。

那么就我当前的问题而言，我需要一个方法，我传入一个引用，在方法中创建所需对象.

那么在Java中就会只能给当前对象在封装一层（定义一个新类），使得需要创建的对象成为新类的成员，在方法中为成员赋值

Example:

C#:

///<summary>

///model

///</summary>

publicclassStudent

{

publicstringName;

publicintAge;

}

///方法:

///<summary>

///错误示范

///

///student这个引用是拷贝传入的，创建新的对应Student

///把引用赋给student，当方法退栈之后student引用回到压栈前

///则Student对象引用数为0，等待GC，引用student依旧是原来的值(逻辑地址)

///</summary>

///<paramname="student"></param>

staticvoidcreateStudent(Studentstudent)

{

student=newStudent{Name="StephenLee",Age=1};

}

///<summary>

///正确做法

///

///通过ref关键字，把操作权让给方法内部

///</summary>

///<paramname="student"></param>

staticvoidcreateStudent(refStudentstudent)

{

student=newStudent{Name="StephenLee",Age=1};

}

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

//Client

staticvoidMain(string[]args)

{

Console.WriteLine("错误示范");

Studentstudent1=null;

createStudent(student1);

if(student1==null)

Console.WriteLine("创建对象失败");

else

Console.WriteLine("创建对象成功,Name:"+student1.Name);

Console.WriteLine("正确做法");

Studentstudent2=null;

createStudent(refstudent2);

if(student2==null)

Console.WriteLine("创建对象失败");

else

Console.WriteLine("创建对象成功,Name:"+student2.Name);

}

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

Java:

/**Model

*@authorStephen

*

*/

publicclassStudent

{

publicStringName;

publicintAge;

publicStudent(Stringname,intage)

{

this.Name=name;

this.Age=age;

}

}

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

/**错误示范,原因同C#

*@paramstudent

*/

privatevoidcreateStudent(Studentstudent)

{

student=newStudent("StephenLee",1);

}

/**正确做法

*@paramstudentPack

*/

privatevoidcreateStudent(StudentPackstudentPack)

{

studentPack.student=newStudent("StephenLee",1);

}

/**包装器

*@authorStephen

*

*/

publicclassStudentPack

{

publicStudentstudent;

}

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

//Client

StudentPackstudentPack=newStudentPack();

createStudent(studentPack);

System.out.println(studentPack.student.Name);

.csharpcode,.csharpcodepre
{
font-size:small;
color:black;
font-family:consolas,"CourierNew",courier,monospace;
background-color:#ffffff;
/*white-space:pre;*/
}
.csharpcodepre{margin:0em;}
.csharpcode.rem{color:#008000;}
.csharpcode.kwrd{color:#0000ff;}
.csharpcode.str{color:#006080;}
.csharpcode.op{color:#0000c0;}
.csharpcode.preproc{color:#cc6633;}
.csharpcode.asp{background-color:#ffff00;}
.csharpcode.html{color:#800000;}
.csharpcode.attr{color:#ff0000;}
.csharpcode.alt
{
background-color:#f4f4f4;
width:100%;
margin:0em;
}
.csharpcode.lnum{color:#606060;}

ref/out关键字:http://msdn.microsoft.com/zh-cn/library/14akc2c7.aspx