How to check if all strings in an array start with upper case letter using forAll?

Question

If I have an array of names, how do I check if they all start with an upper case letter using forall (or something else functional)?

String[] names = {"Linda", "Peter", "Carol", "Paul"};
names.forall(name -> Character.isUpperCase(name.charAt(0)));

that is wrong and I'm not really familiar with higher order functions yet so I could use some help.

`names` is an array, and there is no `forall` method on arrays. — Andreas, Sep 25 '19 at 22:04
You are trying to use forEach function in Java, right? Then use this: ```public static void main(String []args){ String[] names = {"Linda", "Peter", "Carol", "Paul"}; for(String myName : names){ if(Character.isUpperCase(myName.codePointAt(0))){ System.out.println(myName); } } }``` — ken4ward, Sep 25 '19 at 22:23

score 1 · Answer 1 · answered Sep 25 '19 at 22:06

1

Use Stream.allMatch:

String[] names = {"Linda", "Peter", "Carol", "Paul"};
boolean allUpper = Arrays.stream(names).allMatch(name -> Character.isUpperCase(String.codePointAt(0)));

answered Sep 25 '19 at 22:06

Johannes Kuhn

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score 1 · Answer 2 · answered Sep 25 '19 at 22:07

In Java 8+:

Arrays.stream(names).allMatch(name -> Character.isUpperCase(name.codePointAt(0)));

Or:

Stream.of(names).allMatch(name -> Character.isUpperCase(name.codePointAt(0)));

Note that I replaced charAt(0) with codePointAt(0) so it supports Unicode characters in the supplemental planes.

How to check if all strings in an array start with upper case letter using forAll?

2 Answers2