英文:
PrintWriter constructors
问题
我已经列出了 PrintWriter 类的 8 个构造函数。
PrintWriter(File file)，PrintWriter(File file, String csn)，PrintWriter(OutputStream out)，
PrintWriter(OutputStream out, boolean autoFlush)，PrintWriter(String fileName)，
PrintWriter(String fileName, String csn)，PrintWriter(Writer out)，
PrintWriter(Writer out, boolean autoFlush)。
问题：
- 如果没有接受 PrintStream 的 PrintWriter 构造函数，那么我们怎么能够写出像我下面写的语句呢？
- 如果没有接受 BufferedWriter 的 PrintWriter 构造函数，那么我们怎么能够写出像我下面写的语句呢？
PrintWriter writer1 = new PrintWriter(System.out);
PrintWriter writer2;
writer2 = new PrintWriter(new BufferedWriter(new FileWriter(new File(outdir, reportFileName))));
提前感谢您的回答。
英文:
I've listed below the 8 constructors of PrintWriter class.
PrintWriter(File file), PrintWriter(File file, String csn), PrintWriter(OutputStream out),
PrintWriter(OutputStream out, boolean autoFlush), PrintWriter(String fileName),
PrintWriter(String fileName, String csn), PrintWriter(Writer out),
PrintWriter(Writer out, boolean autoFlush).
Questions:
-
If there's no PrintWriter contructor that takes PrintStream, then how come we can write a statment like I've written below?
-
If there's no PrintWriter contructor that takes BufferedWriter, then how come we can write a statment like I've written below?
PrintWriter writer1 = new PrintWriter(System.out); PrintWriter writer2; writer2 = new PrintWriter(new BufferedWriter(new FileWriter(new File(outdir, reportFileName))));
Thanks in advance.
答案1
得分: 2
这是可能的，因为PrintStream继承自FilterOutputStream，而后者再次继承自OutputStream。
一个BufferedWriter继承自Writer。
Writer和OutputStream是PrintWriter构造函数中可能的变量。我们在这里讨论的重要主题是继承。这有一个很好的帖子来解释这个。
英文:
This is possible because PrintStream inherits from FilterOutputStream and the latter again from OutputStream.
A BufferedWriter inherits from Writer.
Writer and OutputStream are possible variables in the PrintWriter constructors. The big topic, what we are talking about here, is inheritance. There is a good post for this.
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