Question

我试图从另一个类中访问一个类中的String。第一节课如下：

import java.sql.*;
import javax.swing.*;
import java.text.SimpleDateFormat;
import java.util.Date;


public class UseData {
Connection connection=null;

public void usePart1Part2(String part1, String part2, String part3, String part4) {
    SimpleDateFormat format = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
    String date = format.format(new Date());

    connection = SQliteConnectionClass.dbconnector();
    try {

        String value1 = part1;   //
        String value2 = part2;   //
        String value3 = part3;   //
        String value4 = part4;   // data need to be used in GenerateSummonPDF.java
        String Timestamp = date;

value1到value4用于以下GenerateSummonPDF类：

public class GenerateSummonPDF {

    public static void main(String[] args) {
        Document document = new Document();
        try {
            PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("C:\\Users\\User\\workspace\\enforement system\\Summon PDF list\\Serial No.pdf"));
            document.open();
            document.add(new Paragraph("the data(value1 to value4 need to print it out here"));  //here is where i need the data
            document.close();
            writer.close();
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

提前感谢您的帮助。

Answer 1

您可以使用吸气剂。以下是作为UseData方法添加的getter的演示：

        public class UseData {

        private String value1;

        public void usePart1Part2(String part1, String part2, String part3, String part4)
        {
            value1 = part1;
        }

        /**
         * Getter for value1
         * @return the value1
         */
        public String getValue1() {
            return value1;
        }

    }

至于从其他类调用getter：

    public class GenerateSummonPDF {

        /**
         * @param args
         */
        public static void main(String[] args) {

            UseData usedata = new UseData();
            String value1 = usedata.getValue1();
        }

    }

Answer 2

    public class UseData {
    private String value1 ;
    private String value2 ;
    private  String value3 ;

// getter- setter for value1 , value2 , value3
// rest of the code.

}

now add modify GenerateSummonPDF as follows :

    public class GenerateSummonPDF {

public static void main(String[] args)
   {
      Document document = new Document();
      try
      {


 PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("C:\\Users\\User\\workspace\\enforement system\\Summon PDF list\\Serial No.pdf"));
         document.open();

          UseData useData = new UseData ();
          useData.usePart1Part2("part1Value" , "part2Value" ,"part3Value" ,"part4Value") ;        

         document.add(new Paragraph("the data("+useData.getValue1()+useData.getValue2()+useData.getValue3()+useData.getValue4()+"));  //here is where i need the data


         document.close();
         writer.close();
      } catch (DocumentException e)
      {
         e.printStackTrace();
      } catch (FileNotFoundException e)
      {
         e.printStackTrace();
      }
   }

然后在你的下一个类中创建对象并从这些方法中获取值像这样的事情

public class usedata { 
   Connection connection=null;
   String value1;   //
   String value2;   //
   String value3;   //
   String value4;  
public void usePart1Part2(String part1, String part2, String part3, String part4)
{
    Date curDate = new Date();
    SimpleDateFormat format = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
    String DateToStr = format.format(curDate);

    connection= SQliteConnectionClass.dbconnector();
try {

   value1 = part1;   //
   value2 = part2;   //
   value3 = part3;   //
   value4 = part4;   // data need to be used in GenerateSummonPDF.java
   String Timestramp = DateToStr;
}

public String getValue1()
{
   return value1;    
} 

public String getValue2()
{
  return value2;    
} 

public String getValue3()
{
  return value3;    
} 

public String getValue4()
{
  return value4;    
}

我希望你能从中得到。快乐学习java

Answer 3

import java.sql.*;
import javax.swing.*;
import java.text.SimpleDateFormat;
import java.util.Date;


public class usedata {
public String part1;
public String part2;
public String part3;
public String part4;
Connection connection=null;

public void usePart1Part2(String part1, String part2, String part3, String part4)
{
this.part1 = part1
this.part2 = part2
this.part3 = part3
this.part4 = part4
Date curDate = new Date();
SimpleDateFormat format = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
        String DateToStr = format.format(curDate);
connection= SQliteConnectionClass.dbconnector();
try {

   String value1 = part1;   //
   String value2 = part2;   //
   String value3 = part3;   //
   String value4 = part4;   // data need to be used in 
   String Timestramp = DateToStr;
....

public class GenerateSummonPDF {

public static void main(String[] args)
   {
      userdata ud = new userdata();
      //you can't acces to the other class attribut
      System.out.println(ud.part1 + ud.part2 + ud.part3 + ud.part4);
      Document document = new Document();
      try
      {
     PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("C:\\Users\\User\\workspace\\enforement system\\Summon PDF list\\Serial No.pdf"));
     document.open();
     document.add(new Paragraph("the data(value1 to value4 need to print it out here"));  //here is where i need the data
     document.close();
     writer.close();
      } catch (DocumentException e)
  {
     e.printStackTrace();
  } catch (FileNotFoundException e)
  {
     e.printStackTrace();
  }
   }

需要使用其他类

4 个答案: