Java作业的麻烦

我正在用两个类编写一个程序。我的

TestState

类需要访问第二个类中的变量，称为

StateBirdAndFlower

要从第一个类读取的资源是一个名为

stateData

的数组，它对应于第二个类

import java.util.Scanner;
import java.util.Arrays;

public class TestState {
    public static void main(String[] args) {
        int position = getInfo(stateData, stateName); 
       //the error is here. stateData is not recogized.
     }
 }
    

这是第二节课：

import java.util.Arrays;

public class StateBirdAndFlower 
{
     String[][] stateData = new String[][] 
     {
        {"Alabama", "Yellowhammer", "Camelia"},
        {"Alaska", "Willow Ptarmigan", "Forget-Me-Not"},
        {"Arizona", "Cactus Wren", "Saguaro Cactus Blossom"},
        {"Arkansas", "Mockingbird", "Apple Blossom"},
        {"California", "California Valley Quail", "Golden Poppy"},
        {"Colorado", "Lark Bunting", "Rocky Mountain Columbine"},
        {"Connecticut", "Robin", "Mountain Laurel"},
        {"Delaware", "Blue Hen Chicken", "Peach Blossom"},
        {"Florida", "Mockingbird", "Orange Blossom"},
        {"Georgia", "Brown Thrasher", "Cherokee Rose"},
        {"Hawaii", "Nene", "Hawaiian Hibiscus"},
        {"Idaho", "Mountain Bluebird", "Syringa, mock orange"},
        {"Illinois", "Cardinal", "Violet"},
        {"Indiana", "Cardinal", "Peony"},
        {"Iowa", "Eastern Goldfinch", "Wild Praire Rose"},
        {"Kansas", "Western Meadowlark", "Sunflower"},
        {"Kentucky", "Cardinal", "Goldenrod"},           
        {"Louisiana", "Eastern Brown Pelican", "Magnolia"},
        {"Maine", "Chickadee", "Pine Cone and Tassel"},
        {"Maryland", "Baltimore Oriole", "Black-Eyed Susan"},
        {"Massachusetts", "Chickadee", "Mayflower"},
        {"Michigan", "Robin", "Apple Blossom"}
      };
}

---

我的问题是，如果位于另一个类上，如何从

TestState

访问此数组？

有很多方法可以做到这一点；显示三个示例：

1。静态变量

在第二个类中，修改

stateData

变量并将其设置为静态：

 public class StateBirdAndFlower {
     //...
     public static String[][] stateData = (...)
     //...
 }

现在，从第一个类调用静态变量：

  int position = getInfo(StateBirdAndFlower.stateData, stateName);

2。Getter方法

创建一个getter方法，这将涉及在代码上实例化

StateBirdAndFlower

类：

public class StateBirdAndFlower 
{
     //...
     public String[][] getStateData()
     {
        return stateData;
     }
     //...
 }

在第一节课上：

public class TestState 
{
   public static void main(String[] args) 
   {
      //...
      StateBirdAndFlower sbf = new StateBirdAndFlower();
      String[][] stateData = sbf.getStateData();
      //...
    }
 }

public class StateBirdAndFlower 
{
     //...
     public static String[][] getStateData()
     {
        return stateData;
     }
     //...
 }

3。静态吸气剂法

您还可以通过从第一个类调用

statebardflower.getStateData（）

将

getStateData

方法声明为静态，并避免重新启动

statebardflower

类：

public class TestState 
{
   public static void main(String[] args) 
   {
      //...
      StateBirdAndFlower sbf = new StateBirdAndFlower();
      String[][] stateData = sbf.getStateData();
      //...
    }
 }

public class StateBirdAndFlower 
{
     //...
     public static String[][] getStateData()
     {
        return stateData;
     }
     //...
 }

在TestClass中：

  int position = getInfo(StateBirdAndFlower.getStateData(), stateName);

---

无论使用哪种方法，请尝试只调用该方法一次（将

stateData

保存到局部变量中，并避免多次调用其他类的方法，即使编译器对此进行了优化）

我看不到对stateBardFlower类的任何引用，该类包含stateData成员变量，在您的第一个代码示例中。我不知道这是否是您的问题，但这肯定是一个改进。在

TestState

类中调用

getInfo（stateData，stateName）StateBirdAndFlower.getInfo（stateData，stateName）取而代之。