2D阵列与1循环的for循环 [英] 2Darray to 1darray with for loop
问题描述
我知道这是一个非常基本的问题,但我只是编程方面的新手而已,我认为我正在为一个非常简单的问题而苦苦挣扎......但是,在这里我们继续:p $ /
在我的应用程序中,我有一个这样的数组的数组存储从MySQL数据库检索的数据。
data_array [] []
0001 | data1 | data2 | data3 | data4 | data5
0002 | data1 | data2 | data3 | data4 | data5
...
...等等。
现在在我的应用程序中,我需要为每个行检索第一个colums,结束类似于:
$ $ p $ 数组{0001,0002}
我知道为迭代做'我可以检索所有的数据:
public String [] itarray {
int cols = 5;
String [] xFINAL; (int j = 0; j xFINAL = data_array [i];
for(int i = 0; i< data_array; i ++)
System.out.println(1+ data_array [i] [0]);
}
System.out.println();
} return xFINAL;}
但是我怎样才能得到每一个行?我试过类似的东西:
int j = 0;
for(int i = 0; i< data_array; i ++){
xFINAL [j] = data_array [i] [0];
j ++;
}
但它给了我一个空指针。我怎么能这样做?
在此先感谢。
String [] xFINAL = new String [data_array.length];
int k = 0;
for(int i = 0; i< data_array; i ++){
array [k ++] = data_array [i] [0];
}
I know this is a very basic question, but I'm just new to programming and I think I'am struggling with a very simple issue... but here we go :p
In my app I have an array of arrays like this storing data retrieved from a mysql database.
data_array[][]
0001 | data1 | data2 | data3 | data4 | data5
0002 | data1 | data2 | data3 | data4 | data5
...
... and so on.
Now in my app, I need to retrieve for each of the rows the first of the colums, ending with something like :
array { 0001, 0002}
I know doing ' for iterations ' I can retrieve all the data:
public String[] itarray{
int cols = 5;
String[] xFINAL;
for (int i=0 ; i < data_array; i++) {
for (int j=0; j < cols; j++){
xFINAL = data_array[i];
System.out.println("1" + data_array[i][0]);
}
System.out.println(" ");
} return xFINAL;}
But how can I get the first column for each of the rows? I tried with something like:
int j=0;
for (int i = 0; i < data_array ; i++){
xFINAL[j] = data_array [i][0];
j++;
}
But it's giving me a null pointer. How could I do this please?
Thanks in advance.
String[] xFINAL = new String[data_array.length];
int k =0;
for (int i=0 ; i < data_array; i++) {
array[k++] = data_array[i][0];
}
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