Creating lots of arrays

How do you create, say, 30 arrays (it doesn't matter of what type, say, char[])? It seems to me that it is not a good idea, to create them one by one by hand. I want to do that using a "for" cycle, but how should I specify identifiers开发者_如何学Python?

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I recommend reading the tutorial on arrays. It covers basic array manipulation, including creation of "multidimensional" arrays.

char[][] arr = new char[30][100];

Now you have arr[0], arr[1], ..., arr[29], each of which is an array of 100 char.

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This snippet shows an example of array initialization and how to access them:

  int[][] m = {
     { 1, 2, 3 },
     { 4, 5, 6, 7, 8 },
     { 9 }
  };
  System.out.println(m[1][3]); // prints "7"

  m[2] = new int[] { -1, -2, -3 };
  System.out.println(m[2][1]); // prints "-2";

This also shows that Java doesn't have true multidimensional arrays; m is really an array of arrays. This means that they can have different lengths ("jagged" arrays), and can be manipulated independently of each other.

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You should also familiarize yourself with java.util.Arrays. It provides utility methods for basic array manipulation (converting to string, copying, sorting, binary search, etc).

  import java.util.Arrays;

  // ...

  int[][] table = new int[3][];
  for (int i = 0; i < table.length; i++) {
      table[i] = new int[i + 1];
      for (int j = 0; j < table[i].length; j++) {
          table[i][j] = (i * 10) + j;
      }
  }
  System.out.println(Arrays.deepToString(table));
  // prints "[[0], [10, 11], [20, 21, 22]]"

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You can always create arrays of arrays:

char[][] arr = new char[30][];
for (int i=0; i<30; i++) {
  arr[i] = new char[50];
}

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I think the easiest way to do it is using an ArrayList

you can put as many items as you want in it:

java.util.ArrayList<char[]> array = new java.util.ArrayList<char[]>();
//set
for(int i=0;i<100;i++){
   array.add(new char[]{'a','b''c'});
}
//get
for(int i=0;i<array.size();i++){
   System.out.println(new String(array.get(i)));
}