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本文我们将了解为什么警告说使用或覆盖已弃用的 API，并演示如何修复此问题以完成任务。

修复警告说使用或覆盖 Java 中已弃用的 API

示例代码（包含警告）：

//import libraries
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

//Main class
public class Main {

 //main method
 public static void main(String[] args){
  //path of a text file
  File filePath = new File("Files/TestFile.txt");
  try {
     //obtain input bytes from a file
     FileInputStream fileInputStream = new FileInputStream(filePath);
     //adds the functionality to another input stream
     BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
     //lets an app read primitive Java data types from the specified input stream
     DataInputStream dataInputStream = new DataInputStream(bufferedInputStream);

     if (dataInputStream.available() != 0) {
        // Get a line.
        String line = dataInputStream.readLine();
        // Place words to an array which are split by a "space".
        String[] stringParts = line.split(" ");
        // Initialize the word's maximum length.
        int maximumLength = 1;

        // iterate over each stingPart, the next one is addressed as "stringX"
        for (String stringX : stringParts) {
           // If a document contains the word longer than.
           if (maximumLength < stringX.length())
              // Set the new value for the maximum length.
              maximumLength = stringX.length();
           }//end for-loop

           // +1 because array index starts from "0".
           int[] counter = new int[maximumLength + 1];
           for (String str : stringParts) {
              // Add one to the number of words that length has
              counter[str.length()] ++;
           }
           // We are using this kind of loop because we require the "length".
           for (int i = 1; i < counter.length; i++) {
              System.out.println(i + " letter words: " + counter[i]);
           }//end for-loop
     }//end if statement
  }//end try
  catch (IOException ex){
     ex.printStackTrace();
  }//end catch
 }//end main method
}//end Main class

在此代码中，我们访问一个 .txt 文件，逐行读取该文件，并将单词放入一个数组中，该数组根据单个空格进行分割。 然后，我们计算每个单词中的字符数并将其全部显示在程序输出中。

尽管该程序生成输出，但它也突出显示我们正在 String line = dataInputStream.readLine(); 行使用或覆盖已弃用的 API。 请参阅以下内容。

此警告是使用 DataInputStream 类的 readLine() 方法生成的。 根据文档，该方法自 JDK 1.1 起已被弃用，因为它不能正确地将字节转换为字符。

尽管该方法已被弃用，但在某些情况下可能会按预期执行。 但我们不能保证它能够继续履行其职责。

因此，最好使用类似但一致的方法。

从 JDK 1.1 开始，读取文本行的首选方法是 BufferedReader 类中的 readLine() 函数。 我们不必从头开始更改所有代码，只需将 DataInputStream 转换为 BufferedReader 类即可。

替换这行代码：

DataInputStream dataInputStream = new DataInputStream(in);

替换为这行代码：

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));

现在，完整的工作程序如下所示。

//import libraries
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;

//Main class
public class Main {

 //main method
 public static void main(String[] args){
  //path of a text file
  File filePath = new File("Files/TestFile.txt");
  try {
     //obtain input bytes from a file
     FileInputStream fileInputStream = new FileInputStream(filePath);
     //adds the functionality to another input stream
     BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
     //lets an app read primitive Java data types from the specified input stream
     //DataInputStream dataInputStream = new DataInputStream(bufferedInputStream);
     BufferedReader bufferedReader = new BufferedReader(
                                     new InputStreamReader(bufferedInputStream));

     String line="";
     //get a line and check if it is not null
     if ((line = bufferedReader. readLine()) != null) {
        // Place words to an array which are split by a "space".
        String[] stringParts = line.split(" ");
        // Initialize the word's maximum length.
        int maximumLength = 1;

        // iterate over each stingPart, the next one is addressed as "stringX"
        for (String stringX : stringParts) {
           // If a document contains the word longer than.
           if (maximumLength < stringX.length())
              // Set the new value for the maximum length.
              maximumLength = stringX.length();
           }//end for-loop

           // +1 because array index starts from "0".
           int[] counter = new int[maximumLength + 1];
           for (String str : stringParts) {
              // Add one to the number of words that length has
              counter[str.length()] ++;
           }
           // We are using this kind of loop because we require the "length".
           for (int i = 1; i < counter.length; i++) {
              System.out.println(i + " letter words: " + counter[i]);
           }//end for-loop
     }//end if statement
  }//end try
  catch (IOException ex){
     ex.printStackTrace();
  }//end catch
 }//end main method
}//end Main class

此外，如果您还看到类似以下内容。

Recompile with -Xlint: deprecation for details

不用担心; 它只是告诉您在编译时使用的选项，以获取有关在何处使用已弃用的内容的更多详细信息。