我想把一个Arraylist转成String[] - 未名空间MITBBS历史存档

我想把一个Arraylist转成String[]# Java - 爪哇娇娃

w*y2004-09-27 07:09

1 楼

假如已经有了一个Arraylist p, 里面的元素其实是一些string
我想转成一个String[]
String[] y = new String[p.size()];
for ( i=0;i< p.size(); i++){
y[i] = (String)p.get(i);
}
可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
怎么回事呢?
我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
这样的, 但是error是 java.lang.ArrayStoreException:((
thx

s*i2004-09-27 07:09

2 楼

(String)(p.get(i))?

);

【在 w***y 的大作中提到】

: 假如已经有了一个Arraylist p, 里面的元素其实是一些string
: 我想转成一个String[]
: String[] y = new String[p.size()];
: for ( i=0;i< p.size(); i++){
: y[i] = (String)p.get(i);
: }
: 可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
: 怎么回事呢?
: 我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
: 这样的, 但是error是 java.lang.ArrayStoreException:((

w*y2004-09-27 07:09

3 楼

I tried that kind of thing, but it didn't help:(

【在 s*i 的大作中提到】

: (String)(p.get(i))?
:
: );

Q*g2004-09-27 07:09

4 楼

你是不是放错东西到p里头了？下面这段是work的
ArrayList p = new ArrayList();
for (int i=0;i<10;i++)
p.add(""+i);
String[] s = new String[p.size()];
for (int i=0;i< p.size(); i++){
s[i] = (String)p.get(i);
}

for (int i=0;iSystem.out.println(s[i]);

【在 w***y 的大作中提到】

: 假如已经有了一个Arraylist p, 里面的元素其实是一些string
: 我想转成一个String[]
: String[] y = new String[p.size()];
: for ( i=0;i< p.size(); i++){
: y[i] = (String)p.get(i);
: }
: 可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
: 怎么回事呢?
: 我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
: 这样的, 但是error是 java.lang.ArrayStoreException:((

xt2004-09-27 07:09

5 楼

唯一的解释是里面那些东西不是String或不全是

【在 w***y 的大作中提到】

: 假如已经有了一个Arraylist p, 里面的元素其实是一些string
: 我想转成一个String[]
: String[] y = new String[p.size()];
: for ( i=0;i< p.size(); i++){
: y[i] = (String)p.get(i);
: }
: 可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
: 怎么回事呢?
: 我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
: 这样的, 但是error是 java.lang.ArrayStoreException:((

xt2004-09-27 07:09

6 楼

Then try p.get(i).toString(). You are guaranteed. :-)

【在 w***y 的大作中提到】

: I tried that kind of thing, but it didn't help:(

w*y2004-09-27 07:09

7 楼

got it, thx a lot:)

【在 xt 的大作中提到】

:
: Then try p.get(i).toString(). You are guaranteed. :-)

xt2004-09-27 07:09

8 楼

You are welcome.
Remember this does not solve your problem, if you intend to use that
ArrayList to store String but you get sth else in it.

【在 w***y 的大作中提到】

: got it, thx a lot:)

c*m2004-09-27 07:09

9 楼

p.get(i).toString() should solve the problem.

);

【在 w***y 的大作中提到】

: 假如已经有了一个Arraylist p, 里面的元素其实是一些string
: 我想转成一个String[]
: String[] y = new String[p.size()];
: for ( i=0;i< p.size(); i++){
: y[i] = (String)p.get(i);
: }
: 可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
: 怎么回事呢?
: 我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
: 这样的, 但是error是 java.lang.ArrayStoreException:((

m*c2004-09-27 07:09

10 楼

Try to print out "p.get(i).getClass().getName()" to debug. You don't want to
find a solution without knowing why :-)

【在 xt 的大作中提到】

:
: You are welcome.
: Remember this does not solve your problem, if you intend to use that
: ArrayList to store String but you get sth else in it.

xt2004-09-27 07:09

11 楼

to
hm... we call that a surprise feature.

【在 m**c 的大作中提到】

:
: Try to print out "p.get(i).getClass().getName()" to debug. You don't want to
: find a solution without knowing why :-)

c*g2004-09-27 07:09

12 楼

String[] predators = al.toArray(new String[0]);

【在 w***y 的大作中提到】

: 假如已经有了一个Arraylist p, 里面的元素其实是一些string
: 我想转成一个String[]
: String[] y = new String[p.size()];
: for ( i=0;i< p.size(); i++){
: y[i] = (String)p.get(i);
: }
: 可是执行到y[i] = (String)p.get(i);总是有 java.lang.ClassCastException
: 怎么回事呢?
: 我还试了String[] predators = (String[])al.toArray( new String[ al.size() ] );
: 这样的, 但是error是 java.lang.ArrayStoreException:((

m*t2004-09-27 07:09

13 楼

This has got to be the worst solution I have ever seen _you_ giving on this
board, man. 8-)

【在 xt 的大作中提到】

:
: to
: hm... we call that a surprise feature.

xt2004-09-27 07:09

14 楼

Come on, woomy was so desparate so I gave out this horrible stuff to let it
at least run. :-)
Then he can find out what is going wrong by looking at the strings.

【在 m******t 的大作中提到】

:
: This has got to be the worst solution I have ever seen _you_ giving on this
: board, man. 8-)

m*t2004-09-27 07:09

15 楼

this
Right, that's the part I rarely see people do once they got around a problem.
8-)

【在 xt 的大作中提到】

:
: Come on, woomy was so desparate so I gave out this horrible stuff to let it
: at least run. :-)
: Then he can find out what is going wrong by looking at the strings.