Java 如何在printf中对齐字符串？

正如我们所知，在格式化打印时，我们可以确定对齐方式和小数点的数量，例如：

    System.out.printf( "%9.2f", total );
     System.out.printf( "%-20s", name );
     System.out.printf( "%8s", adress );

但是我怎样才能用字符串表示呢？？ 此代码用于显示手术期间给患者的药物剂量表，我使用joptionpane.showMessageDialog打印字符串表示，无法修复对齐问题，以下代码为：

 public class DrugsTable
   {

   private String patientName; // name of the patient
  private int doses[][]; // two-dimensional array of patient doses
  private String opDrugs []={"O2","N2O","gas","musle     
   relaxent","narcotic","fluid","atropine","neostagmine"};
   String str = "";
   // two-argument constructor initializes patientName and doses array
   public DrugsTable( String name, int dosesArray[][] )
   {
  patientName = name; // initialize patientName
  doses = dosesArray; // store doses
   } // end two-argument DrugsTable constructor

   // method to set the patient name
   public void setPatientName( String name )
   {
  patientName = name; // store the course name
   } // end method setPatientName

   // method to retrieve the patient name
   public String getPatientName()
  {
  return patientName;
   } // end method getPatientName

   // display a welcome message to the user
   public void displayMessage()
   {
  // getpatientName gets the name of the course
     str +="Welcome;\n"+getPatientName()+"\n\n"; 

    } // end method displayMessage

   // perform various operations on the data
    public void processDoses()
    {
  // output doses array
  outputdoses();  
    } // end method processdoses

     // determine Total dose given during operation
   public double getTotal( int setOfdoses[] )
   {      
      int total = 0; // initialize total

     // sum doses for one drug
      for ( int dose1 : setOfdoses )
     total += dose1;

     // return total of doses
      return (double)total ;
     } // end method getTotal


     // output the contents of the doses array
     public void outputdoses()
     {
        str+="            "; // align column heads

       // create a column heading for each time

       str +="\t"+"Time1   "+"Time2   "+"Time3";

        str+="   Total\n"; // total dose column heading

      // create rows/columns of text representing array doses
       for ( int drug = 0; drug < doses.length; drug++ ) 
      {
     str +=opDrugs[drug]; //getText

     for ( int dose : doses[ drug ] ) // output patient's doses
        str +="        "+String.valueOf(dose);

     // call method getTotal to calculate drug's total dose;
     // pass row of doses as the argument to getTotal
     double total = getTotal( doses[ drug ] );
       str +="        "+String.valueOf(total)+"\n";
       } // end outer for
    } // end method outputdoses


 } // end class DrugsTable

---

您正在寻找吗？您的第二个示例

System.out.printf（“%-20s”，name）

用于字符串表示-为什么不使用它？@geert3我把它作为printf的一个示例，它不在代码中

import javax.swing.JOptionPane;
 public class DrugsTableTest
  {
    public static void main( String args[] )
    {
    // two-dimensional array of drugs doses given during operation
       int drugDosesArray[][] = { { 99, 96, 70 },
                          { 68, 87, 90 },
                          { 94, 100, 90 },
                          { 100, 81, 82 },
                          { 83, 65, 85 },
                          { 78, 87, 65 },
                          { 85, 75, 83 }, 
                          { 91, 94, 100 }};

      DrugsTable drugsTable = new DrugsTable( 
     "drugs given during operation are:", drugDosesArray );
  drugsTable.displayMessage();
  drugsTable.processDoses();
  JOptionPane.showMessageDialog(null,drugsTable.str);

   } // end main
} // end class DrugsTableTest