☕ JAVA TRICK: Boolean expression in Pattern Matching

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☕ JAVA TRICK: Boolean expression in Pattern Matching

· java

You know pattern matching, but did you know that you can use the variable it introduces in the same boolean expression?

If you check whether the instance '𝐨𝐛𝐣𝐞𝐜𝐭' is of type '𝐒𝐭𝐫𝐢𝐧𝐠' with '𝐨𝐛𝐣𝐞𝐜𝐭 𝐢𝐧𝐬𝐭𝐚𝐧𝐜𝐞𝐨𝐟 𝐒𝐭𝐫𝐢𝐧𝐠 𝐬',

you can start using '𝐬' straight away, for example to check whether it's non-empty with '&& !𝐬.𝐢𝐬𝐄𝐦𝐩𝐭𝐲()'.

Object object = ...; // any object
if (object instanceof String s && !s.isEmpty()) {
  int length = s.length();
  System.out.println("This object is a non-empty string of length " + length);
} else {
  System.out.println("This object is not a string.");
}

This works in '𝐢𝐟' statements in 𝐉𝐚𝐯𝐚 𝟏𝟔 and in '𝐬𝐰𝐢𝐭𝐜𝐡' as a preview in 𝐉𝐚𝐯𝐚 𝟏𝟕.

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