Can't return a Object[] casted as String[]

Question

public String[] getAllKeys (){

    Object[] keysCopy = new Object[keys.size()];
    keysCopy = keys.toArray();

    return ((String[])keysCopy());
}

Why this gives me Ljava.lang.Object; cannot be cast to [Ljava.lang.String??

possible duplicate of [java: (String\[\])List.toArray() gives ClassCastException](http://stackoverflow.com/questions/5690351/java-stringlist-toarray-gives-classcastexception) — Alexis C., Apr 24 '14 at 09:25

sanbhat · Accepted Answer · 2014-04-24T09:37:15.380

2

It is because you have object array and Object[] cannot be cast to String[]. The reverse is possible. Its because Object IS NOT A String and String IS A Object.

If you are sure that the content of keys is collection of String, then you can use keys.toArray(new String[keys.size()]);

public String[] getAllKeys(){
    return keys.toArray(new String[keys.size()]);
}

edited Apr 24 '14 at 09:37

answered Apr 24 '14 at 09:27

sanbhat

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Or in case of Streams: `keys.stream().toArray(String[]::new)`. – andy Oct 16 '20 at 14:53

score 0 · Answer 2 · answered Apr 24 '14 at 09:27

0

`return Arrays.copyOf(keysCopy, keysCopy.length, String[].class);`

answered Apr 24 '14 at 09:27

sadhu

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score 0 · Answer 3 · answered Apr 24 '14 at 09:28

0

An Object[] is not a String[].

answered Apr 24 '14 at 09:28

Bohemian

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score 0 · Answer 4 · edited May 23 '17 at 10:26

0

Try this, it works.

public String[] getAllKeys (){
Object[] keysCopy = new Object[keys.size()];
keysCopy = keys.toArray(new String[0]);
return (String[]) keysCopy;
}

For more you can read this [post] (How to convert object array to string array in Java)

edited May 23 '17 at 10:26

Community

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answered Apr 24 '14 at 09:58

Ankit

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Can't return a Object[] casted as String[]

4 Answers4