在Java中声明变量之前，给另一个类variablevalues_Java_Variables

在Java中声明变量之前，给另一个类variablevalues

java variables

在Java中声明变量之前，给另一个类variablevalues,java,variables,Java,Variables,我试图将值传递给可能尚未声明的变量。在我的主要源类中，我给了另一个类一些值，但后来这些值似乎消失了源代码： server.java（主）： public class server { public static void main(String[] args) { //Print a simple message to the user to notify there is something going on... System.out.println("Starti

我试图将值传递给可能尚未声明的变量。在我的主要源类中，我给了另一个类一些值，但后来这些值似乎消失了

源代码： server.java（主）：

public class server {

public static void main(String[] args)  {

    //Print a simple message to the user to notify there is something going on...
    System.out.println("Starting server, please wait...");

    //Connecting all class files to the server.
    filehandler filehandlerclass = new filehandler();
    networking networkingclass = new networking();
    //End of class files connecting.

    //Preparing the filehandler's file information to open a new filestream.
    filehandlerclass.filetohandlename = "server";
    filehandlerclass.filetohandleextention = "ini";
    filehandlerclass.filetohandlepath = "configs\\";

    //Request a new filestream using the filehandler's file variables.
    filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);

    //Checks if the filehandler has tried to open a filestream.
    if(filehandlerclass.filestreamopen == true) {
        //Request a check if the filestream was opened sucessfully.
        filehandlerclass.filestreamexists(filehandlerclass.filestream);
    }
    //If the filehandler has not tried to open a filestream...
    else    {
        System.out.println("Error: The filehandler does not seem to have tried to open a filoestream yet.");
        System.out.println("A possibility is that the server could not call the method from the filehandler properly.");
    }

    //Checks if the boolean "filestreamexists" from the filehandlerclass is true.
    if(filehandlerclass.filestreamexists(filehandlerclass.filestream) == true)  {
        //The filestream seems to exist, let's read the file and extract it's information.
        filehandlerclass.readfile(filehandlerclass.filestream);
    }
    else    {
        filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);
    }
}
}

//Imports the java.io library so the filehandler can read and write to text files.
import java.io.*;

public class filehandler    {

//Variables for the filehandler class.
public String filetohandlename;
public String filetohandleextention;
public String filetohandlefullname = filetohandlename + "." + filetohandleextention;
public String filetohandlepath;
public String filetohandle = filetohandlepath + filetohandlefullname;

//Boolean that is true if the filehandler's "openfilestream"-method has tried to open a filestream.
//Is false as long as none filestreams have been touched.
public boolean filestreamopen = false;

//Declares a variable for the filestream to access text files.
public File filestream;
//End of variable list.

//Called to open a filestream so the server can load properties from text files.
public void openfilestream(File filestream, String filetohandle)    {

    //Tell the user that a filestream is about to be opened.
    System.out.println("Opening filestream for \"" + filetohandlefullname + "\"...");
    //Open a filestream called "filestream" using the variable "filetohandle"'s value
    //as information about wich file to open the filestream for.
    filestream = new File(filetohandle);
    //Turn the boolean "filestreamopen" to true so next time the server checks it's
    //value, it knows if the filehandler has tried to open a filestream.
    filestreamopen = true;
}

//Boolean that checks if the filestream exists.
public boolean filestreamexists(File filestream)    {
    //Tell the user that a check on the filestream is going on.
    System.out.println("Checking if filestream for \"" + filetohandlefullname + "\" exists...");
    //If the filestream exists...
    if(filestream.exists()) {
        //Tell the user that the filestream exists.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" exists!");
        //Make the boolean's value positive.
        return true;
    }
    //If the filestream does not exist...
    else    {
        //Tell the user that the filestream does not exist.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" does not exist!");
        //Make the boolean's value negative.
        return false;
    }
}

//Called to read files and collect it's information.
public void readfile(File filestream)   {
    //Checks if the file that is going to be read is a configuration file.
    if(filetohandleextention == "ini")  {
        //Tell the user that a configuration file is going to be read.
        System.out.println("Extracting information from the configuration file \"" + filetohandle + "\".");
    }
}
}

public class networking {

}

filehandler.java:

public class server {

public static void main(String[] args)  {

    //Print a simple message to the user to notify there is something going on...
    System.out.println("Starting server, please wait...");

    //Connecting all class files to the server.
    filehandler filehandlerclass = new filehandler();
    networking networkingclass = new networking();
    //End of class files connecting.

    //Preparing the filehandler's file information to open a new filestream.
    filehandlerclass.filetohandlename = "server";
    filehandlerclass.filetohandleextention = "ini";
    filehandlerclass.filetohandlepath = "configs\\";

    //Request a new filestream using the filehandler's file variables.
    filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);

    //Checks if the filehandler has tried to open a filestream.
    if(filehandlerclass.filestreamopen == true) {
        //Request a check if the filestream was opened sucessfully.
        filehandlerclass.filestreamexists(filehandlerclass.filestream);
    }
    //If the filehandler has not tried to open a filestream...
    else    {
        System.out.println("Error: The filehandler does not seem to have tried to open a filoestream yet.");
        System.out.println("A possibility is that the server could not call the method from the filehandler properly.");
    }

    //Checks if the boolean "filestreamexists" from the filehandlerclass is true.
    if(filehandlerclass.filestreamexists(filehandlerclass.filestream) == true)  {
        //The filestream seems to exist, let's read the file and extract it's information.
        filehandlerclass.readfile(filehandlerclass.filestream);
    }
    else    {
        filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);
    }
}
}

//Imports the java.io library so the filehandler can read and write to text files.
import java.io.*;

public class filehandler    {

//Variables for the filehandler class.
public String filetohandlename;
public String filetohandleextention;
public String filetohandlefullname = filetohandlename + "." + filetohandleextention;
public String filetohandlepath;
public String filetohandle = filetohandlepath + filetohandlefullname;

//Boolean that is true if the filehandler's "openfilestream"-method has tried to open a filestream.
//Is false as long as none filestreams have been touched.
public boolean filestreamopen = false;

//Declares a variable for the filestream to access text files.
public File filestream;
//End of variable list.

//Called to open a filestream so the server can load properties from text files.
public void openfilestream(File filestream, String filetohandle)    {

    //Tell the user that a filestream is about to be opened.
    System.out.println("Opening filestream for \"" + filetohandlefullname + "\"...");
    //Open a filestream called "filestream" using the variable "filetohandle"'s value
    //as information about wich file to open the filestream for.
    filestream = new File(filetohandle);
    //Turn the boolean "filestreamopen" to true so next time the server checks it's
    //value, it knows if the filehandler has tried to open a filestream.
    filestreamopen = true;
}

//Boolean that checks if the filestream exists.
public boolean filestreamexists(File filestream)    {
    //Tell the user that a check on the filestream is going on.
    System.out.println("Checking if filestream for \"" + filetohandlefullname + "\" exists...");
    //If the filestream exists...
    if(filestream.exists()) {
        //Tell the user that the filestream exists.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" exists!");
        //Make the boolean's value positive.
        return true;
    }
    //If the filestream does not exist...
    else    {
        //Tell the user that the filestream does not exist.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" does not exist!");
        //Make the boolean's value negative.
        return false;
    }
}

//Called to read files and collect it's information.
public void readfile(File filestream)   {
    //Checks if the file that is going to be read is a configuration file.
    if(filetohandleextention == "ini")  {
        //Tell the user that a configuration file is going to be read.
        System.out.println("Extracting information from the configuration file \"" + filetohandle + "\".");
    }
}
}

public class networking {

}

networking.java:

public class server {

public static void main(String[] args)  {

    //Print a simple message to the user to notify there is something going on...
    System.out.println("Starting server, please wait...");

    //Connecting all class files to the server.
    filehandler filehandlerclass = new filehandler();
    networking networkingclass = new networking();
    //End of class files connecting.

    //Preparing the filehandler's file information to open a new filestream.
    filehandlerclass.filetohandlename = "server";
    filehandlerclass.filetohandleextention = "ini";
    filehandlerclass.filetohandlepath = "configs\\";

    //Request a new filestream using the filehandler's file variables.
    filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);

    //Checks if the filehandler has tried to open a filestream.
    if(filehandlerclass.filestreamopen == true) {
        //Request a check if the filestream was opened sucessfully.
        filehandlerclass.filestreamexists(filehandlerclass.filestream);
    }
    //If the filehandler has not tried to open a filestream...
    else    {
        System.out.println("Error: The filehandler does not seem to have tried to open a filoestream yet.");
        System.out.println("A possibility is that the server could not call the method from the filehandler properly.");
    }

    //Checks if the boolean "filestreamexists" from the filehandlerclass is true.
    if(filehandlerclass.filestreamexists(filehandlerclass.filestream) == true)  {
        //The filestream seems to exist, let's read the file and extract it's information.
        filehandlerclass.readfile(filehandlerclass.filestream);
    }
    else    {
        filehandlerclass.openfilestream(filehandlerclass.filestream, filehandlerclass.filetohandle);
    }
}
}

//Imports the java.io library so the filehandler can read and write to text files.
import java.io.*;

public class filehandler    {

//Variables for the filehandler class.
public String filetohandlename;
public String filetohandleextention;
public String filetohandlefullname = filetohandlename + "." + filetohandleextention;
public String filetohandlepath;
public String filetohandle = filetohandlepath + filetohandlefullname;

//Boolean that is true if the filehandler's "openfilestream"-method has tried to open a filestream.
//Is false as long as none filestreams have been touched.
public boolean filestreamopen = false;

//Declares a variable for the filestream to access text files.
public File filestream;
//End of variable list.

//Called to open a filestream so the server can load properties from text files.
public void openfilestream(File filestream, String filetohandle)    {

    //Tell the user that a filestream is about to be opened.
    System.out.println("Opening filestream for \"" + filetohandlefullname + "\"...");
    //Open a filestream called "filestream" using the variable "filetohandle"'s value
    //as information about wich file to open the filestream for.
    filestream = new File(filetohandle);
    //Turn the boolean "filestreamopen" to true so next time the server checks it's
    //value, it knows if the filehandler has tried to open a filestream.
    filestreamopen = true;
}

//Boolean that checks if the filestream exists.
public boolean filestreamexists(File filestream)    {
    //Tell the user that a check on the filestream is going on.
    System.out.println("Checking if filestream for \"" + filetohandlefullname + "\" exists...");
    //If the filestream exists...
    if(filestream.exists()) {
        //Tell the user that the filestream exists.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" exists!");
        //Make the boolean's value positive.
        return true;
    }
    //If the filestream does not exist...
    else    {
        //Tell the user that the filestream does not exist.
        System.out.println("Filestream for \"" + filetohandlefullname + "\" does not exist!");
        //Make the boolean's value negative.
        return false;
    }
}

//Called to read files and collect it's information.
public void readfile(File filestream)   {
    //Checks if the file that is going to be read is a configuration file.
    if(filetohandleextention == "ini")  {
        //Tell the user that a configuration file is going to be read.
        System.out.println("Extracting information from the configuration file \"" + filetohandle + "\".");
    }
}
}

public class networking {

}

问题： java将为源文件提供命令，并告诉它们该做什么。除非server.java给了源文件一个命令，否则源文件不会自行运行。通过这种方式，我计划能够在server.java中编写简单的函数调用，以便从不同的源文件执行更大的任务

在声明变量之前，server.java似乎传递变量“filetohandlename”、“filetohandleextention”和“filetohandlepath”，在声明变量时，它们的值为“null”

结果：

我编译它时没有错误。我认为现在正在发生的是一个错误匹配，它给出了指定要读取的文件的正确值的变量。它还抛出了一个我现在还没有仔细研究过的异常，要么是因为“null.null”不存在，要么是因为我写错了代码

最终请求： 有人知道我是否可以制作一个接收变量值的方法吗或者是否有其他更合适的方法？我可以在server.java中创建一个变量数组并从该数组中收集值吗

非常感谢您抽出时间。

这：

public String filetohandlename;
public String filetohandleextention;
public String filetohandlefullname = filetohandlename + "." + filetohandleextention;

将前两个变量初始化为null，将第三个变量初始化为“null.null”。请注意，如果更改组成

filetohandlefullname

的组件变量之一，则不会更改

filetohandlefullname

的值。如果希望发生这种情况，则应将

filetohandlefullname

替换为执行追加操作的方法

这：

将不同的变量

filetohandle

传递到方法中。该变量不同于

this.filetohandle

我认为这段代码（上面）有很多问题，我会做以下工作

用动态执行此操作的方法替换通过其他变量实例化的变量。这样，当您更改

var1

时，您希望更改

var2

的值，这将通过方法返回自动发生。e、 g创建一个私有方法

getFileToHandleFullName（）

并保存相应的变量

使用

此

在可能的情况下，将这些成员设置为final，这样您就不会无意中更改它们

这：

将前两个变量初始化为null，将第三个变量初始化为“null.null”。请注意，如果更改组成

filetohandlefullname

的组件变量之一，则不会更改

filetohandlefullname

的值。如果希望发生这种情况，则应将

filetohandlefullname

替换为执行追加操作的方法

这：

将不同的变量

filetohandle

传递到方法中。该变量不同于

this.filetohandle

我认为这段代码（上面）有很多问题，我会做以下工作

用动态执行此操作的方法替换通过其他变量实例化的变量。这样，当您更改

var1

时，您希望更改

var2

的值，这将通过方法返回自动发生。e、 g创建一个私有方法

getFileToHandleFullName（）

并保存相应的变量

使用

此

在可能的情况下，将这些成员设置为final，这样您就不会无意中更改它们

这条线

public String filetohandlefullname = filetohandlename + "." + filetohandleextention;

在实例化类时执行（即

filehandler filehandlerclass=new filehandler（）；

）。此时两个变量都未设置，因此

filetohandlefullname

被初始化为

null.null

但是你的代码还有很多其他的问题，比如

//Request a new filestream using the filehandler's file variables.
filehandlerclass.openfilestream(filehandlerclass. filestream,filehandlerclass.filetohandle);

例如，您传递的参数是来自同一实例的字段。这是完全无用的，因为该方法已经可以访问这些内容，而且非常混乱

也许有点争议：

//Make the boolean's value positive.
return true;

注释只有在澄清代码时才有用，如果没有注释，代码就不那么明显，并且注释必须100%真实，而不是像经常发生的那样，程序希望代码做什么。在这种特定情况下，这两个条件都不满足，因为注释没有说明发生了什么，实际上方法的返回值是设置的，而不是这一行中一些不起眼的“布尔值”

public String filetohandlefullname = filetohandlename + "." + filetohandleextention;