Javadoc Puzzlers of the Day

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Java(doc) Puzzlersof the Day

• Roger Lindsjö, Ericsson

Tack till Joshua Bloch, Neil Gafter
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Perfekt Hash
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Vad blir utskriften?
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(No Transcript)
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Hmm
Kan returnera negativa svar
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Math.abs
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Vad blir utskriften?
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(No Transcript)
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Math.abs Javadoc

• public static int abs(int a) Returns the absolute
  value of an int value.
• If the argument is not negative, the argument is
  returned. If the argument is negative, the
  negation of the argument is returned.
• Note that if the argument is equal to the value
  of Integer.MIN_VALUE, the most negative
  representable int value, the result is that same
  value, which is negative.

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Väl valda värden
läsa.hashCode() installeras.hashCode()
Integer.MIN_VALUE
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Unika URLer
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Vad blir utskriften?
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Alla rätt
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URL.equals Javadoc

• Two hosts are considered equivalent if both host
  names can be resolved into the same IP addresses
  else if either host name can't be resolved, the
  host names must be equal without regard to case
  or both host names equal to null.
• Since hosts comparison requires name resolution,
  this operation is a blocking operation.
• Note The defined behavior for equals is known to
  be inconsistent with virtual hosting in HTTP.

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Sensmoralen

• Läs Javadoc innan du använder metoden första
  gången. Den kanske inte gör vad du tror.
• Testa gränsvärden.

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Manage name resolving

• http//java.sun.com/javase/6/docs/technotes/guides
  /net/properties.html
• Codejava.security.Security.setProperty("networkad
  dress.cache.ttl" , "0")
• Commandline-Dsun.net.inetaddr.ttl0