I have four arrays of strings and I would like to create a two dimensional array of 3 columns and dynamic rows.
the arrays are like:
String[] first_name; String[] last_name; String[] unit; String[] phone_number; Object[][] obj = new Object[first_name.length()][3] My problem is how do I achieve something like this:
obj = {first_name[index] + " " + last_name[index], unit[index], phone_number[index]} Please help out!!!
I am assuming that by dynamic rows you mean that it depends on the number of elements in the first_name array.
So you could simply iterate:
String[][]obj = new String[first_name.length][3]; for (int i = 0; i < first_name.length; i++) { obj[i][0] = first_name[i] + " " + last_name[i]; obj[i][1] = unit[i]; obj[i][2] = phone_number[i]; } However, this approach is not very good. You should consider creating an object for example named Employee which as the 3 fields, and then you just have an array of Employee
For example:
public class Employee { String name; String unit; String phoneNumber; public Employee(String name, String unit, String phoneNumber) { //... rest of constructor to copy the fields } //... setters and getters } And then you just have:
Employee[] employees = new Employee[first_name.length]; for (int i = 0; i < first_name.length; i++) { employees[i] = new Employee(first_name[i] + " " + last_name[i], unit[i], phone_number[i]); } Would this help?
int len = first_name.lenghth(); String[][] arr2d = new String[len][3]; for (int i=0; i < len; i++) { arr2d[i][0] = first_name[i] + " " + last_name[i]; arr2d[i][1] = unit[i]; arr2d[i][2] = phone_number[i]; } 
this could be what you are looking for: (Assume that the four arrays have same length)
String[][] result = new String[first_name.length][3]; for(int i =0; i<first_name.length;i++){ result[i][0]=first_name[i]+" "+last_name[i]; result[i][1]=unit[i]; result[i][2]=phone_number[i]; } 
String[] first_name = new String[length]; String[] last_name = new String[length];//length means your length of string String[] unit = new String[length]; String[] phone_number = new String[length]; Object[][] obj = new Object[first_name.length][3]; for(int index =0;index<first_name.length;index++){ obj[index][0] = first_name[index] + " " + last_name[index]; obj[index][1] = unit[index]; obj[index][2] = phone_number[index]; } 
There are a couple of ways to make 3-D arrays.
I would avoid Object[][], I never like the handling or performance.
Since a 3-D array is just an array of arrays, an easy approach would to use the List data structure. List[] or List> should do the trick. This way you have all the built-ins of a Collection object plus you can also Apache commons, lambdaJ or Guava on top of it.
If you are dead set on using primitive arrays then you could also make a regular 2-D array, [], that can act like a 3-D array, [][].
Here is simple wrapper method I made around a basic array that will function the same as 3-D array.
public class MyThreeDArray{ int MAX_ROW; int MAX_COL; int[] arr; public MyThreeDArray(final int MAX_ROW, final int MAX_COL){ this.MAX_ROW = MAX_ROW; this.MAX_COL = MAX_COL; arr = new int[MAX_ROW * MAX_COL]; } private int findIndex(int row, int col) throws IllegalArgumentException{ if(row < 0 && row >= MAX_ROW ){ throw new IllegalArgumentException("Invaild row value"); } if(col < 0 && col >= MAX_COL ){ throw new IllegalArgumentException("Invaild col value"); } return ( row * MAX_COL + col ); } public int get(int row, int col){ return arr[findIndex(row, col)]; } public void set(int row, int col, int value){ arr[findIndex(row, col)] = value; } } Also keep in mind I never tested any of this.
So if you did this with Strings then row 0 might contain the first name values, ... and row 4 could have the unit values.
To retrieve person A's data with this wrapper could make a call similar to this:
String firstName = myWrapper.get(0,0); String lastName = myWrapper.get(0,1); String phone = myWrapper.get(0,2); String unit = myWrapper.get(0,3); And person B's data would be stored in the second row.
But why try to combine arrays together? You could easy make a POJO called person
public class Person{ String firstName; String lastName; String phone; String unit; public Person(){} //ToDo: Getters and Setters } This way could just easily add validation and clearly call a specific person without any trouble.
Person[] customers = new Person[5]; or better yet
List<Person> customers = new ArrayList<Person>(); 
List