构建器[Java编程]

//: Cleanup.java
// Paying attention to exceptions
// in constructors
import java.io.*;

class InputFile {
  private BufferedReader in;
  InputFile(String fname) throws Exception {
    try {
      in = 
        new BufferedReader(
          new FileReader(fname));
      // Other code that might throw exceptions
    } catch(FileNotFoundException e) {
      System.out.println(
        "Could not open " + fname);
      // Wasn't open, so don't close it
      throw e;
    } catch(Exception e) {
      // All other exceptions must close it
      try {
        in.close();
      } catch(IOException e2) {
        System.out.println(
          "in.close() unsuccessful");
      }
      throw e;
    } finally {
      // Don't close it here!!!
    }
  }
  String getLine() {
    String s;
    try {
      s = in.readLine();
    } catch(IOException e) {
      System.out.println(
        "readLine() unsuccessful");
      s = "failed";
    }
    return s;
  }
  void cleanup() {
    try {
      in.close();
    } catch(IOException e2) {
      System.out.println(
        "in.close() unsuccessful");
    }
  }
}

public class Cleanup {
  public static void main(String[] args) {
    try {
      InputFile in = 
        new InputFile("Cleanup.java");
      String s;
      int i = 1;
      while((s = in.getLine()) != null)
        System.out.println(""+ i++ + ": " + s);
      in.cleanup();
    } catch(Exception e) {
      System.out.println(
        "Caught in main, e.printStackTrace()");
      e.printStackTrace();
    }
  }
} ///:~