这是一个我无法完成的考试问题。
This was an exam question which I couldn't complete.
如何获得以下java代码进行打印错误仅在 MyClass 构造函数中编辑代码?
How do you get the following java code to print false by only editing code within the MyClass constructor? public class MyClass{ public MyClass(){ } public static void main(String[] args) { MyClass m = new MyClass(); System.out.println(m.equals(m)); } }
您不能覆盖等于方法,或者在主方法中更改中的任何一个代码。代码必须在没有程序崩溃的情况下运行。
You are NOT allowed to override the equals method, or change any of the code within the main method. The code must run without the program crashing.
根据我的研究,你不能设置Java对象引用在实例化类时为null。所以我正式难倒。
According to my research, you can't set a Java object reference to null when you instantiate a class. So I'm officially stumped.
推荐答案这很难!!
public MyClass() { System.setOut(new PrintStream(new FilterOutputStream(System.out) { @Override public void write(byte[] b, int off, int len) throws IOException { if(new String(b).contains("true")) { byte[] text = "false".getBytes(); super.write(text, 0, text.length); } else { super.write(b, off, len); } } }, true)); }
或Paul Boddington的简化版:
Or Paul Boddington's simplified version:
PrintStream p = System.out; System.setOut(new PrintStream(p) { @Override public void println(boolean b) { p.println(false); } });更多推荐
使用类构造函数处理Java对象引用
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