java - 如何在java中返回一个可由其他对象访问的数组？

Question

我想在读取文本文件后返回一个可由其他对象访问的数组。我的指令解析类是:

import java.io.*;

public class Instruction {
   public String[] instructionList;

   public String[] readFile() throws IOException {
      FileInputStream in = new FileInputStream("directions.txt");
      BufferedReader br = new BufferedReader(new InputStreamReader(in));

      int n = 5;
      instructionList = new String[n];

      for (int j = 0; j < instructionList.length; j++) {
          instructionList[j] = br.readLine();
      }
      in.close();   
      return instructionList;
  }

}

上面的代码接收一个包含 5 行文本的文本文件。在我的 main() 中，我想运行该函数并使字符串数组可供其他对象访问。

import java.util.Arrays;
public class RoverCommand {

  public static void main(String[] args) throws Exception {
      Instruction directions = new Instruction();
      directions.readFile();

      String[] directionsArray;
      directionsArray = directions.returnsInstructionList();

      System.out.println(Arrays.toString(directionsArray));
  }

}

最好的方法是什么？如果数组的元素是数字，我需要整数；如果它们是字母，我需要字符串。附:我是 Java 新手。有更好的方法来做我正在做的事情吗？

Answer 1

您不必使用泛型。我 try catch 访问器中的异常，并在出现任何问题时返回 null。因此您可以在继续之前测试返回的值是否为 null。

// Client.java
import java.io.IOException;

public class Client {
    public static void main(String args[]) {
        try {
            InstructionList il = new InstructionList();
            il.readFile("C:\\testing\\ints.txt", 5);

            int[] integers = il.getInstructionsAsIntegers();

            if (integers != null) {
                for (int i : integers) {
                    System.out.println(i);
                }
            }
        } catch (IOException e) {
            // handle
        }
    }
}


// InstructionList.java
import java.io.*;

public class InstructionList {
    private String[] instructions;

    public void readFile(String path, int lineLimit) throws IOException {
        FileInputStream in = new FileInputStream(path);
        BufferedReader br = new BufferedReader(new InputStreamReader(in));

        instructions = new String[lineLimit];

        for (int i = 0; i < lineLimit; i++) {
            instructions[i] = br.readLine();
        }

        in.close();
    }

    public String[] getInstructionsAsStrings() {
        return instructions; // will return null if uninitialized
    }

    public int[] getInstructionsAsIntegers() {
        if (this.instructions == null) {
            return null;
        }

        int[] instructions = new int[this.instructions.length];

        try {
            for (int i = 0; i < instructions.length; i++) {
                instructions[i] = new Integer(this.instructions[i]);
            }
        } catch (NumberFormatException e) {
            return null; // data integrity fail, return null
        }

        return instructions;
    }
}