Java中的自定义数组列表

Arraylist<DataType> al = new ArrayList<Datatype> ;


ArrayList <E> list = new ArrayList <> ();


ArrayList<Integer> al = new Arraylist<Integer>() ;
al.add(1) ;


ArrayList alobj = new Arraylist() ;
alobj(new Integer(1)) ;


ArrayList<Integer> roll = new ArrayList<>(); // roll number


ArrayList<String> name = new ArrayList<>(); // name


ArrayList<Integer> marks = new ArrayList<>(); // marks


ArrayList<Long> phone = new ArrayList<>(); // phone number


for (int i = 0; i < n; i++)
{
// Adding all the values to each arraylist
// each arraylist has primitive datatypes
roll.add(rollnum_i);
name.add(name_i);
marks.add(marks_i);
phone.add(phone_i);
}


// Java program to illustrate Custom ArrayList
// Importing ArrayList class from java.util package
import java.util.ArrayList;
// Class 1
// Outer class
// Main class
// CustomArrayList
class GFG {
    // Custom class which has data type class has
    // defined the type of data ArrayList
    // size of input 4
    int n = 4;
    // Class 2
    // Inner class
    // The custom datatype class
    class Data {
        // Global variables of the class
        int roll;
        String name;
        int marks;
        long phone;
        // Constructor has type of data that is required
        Data(int roll, String name, int marks, long phone)
        {
            // Initialize the input variable from main
            // function to the global variable of the class
            // this keyword refers to current instance
            this.roll = roll;
            this.name = name;
            this.marks = marks;
            this.phone = phone;
        }
    }
    // Method 1
    // Main driver method
    public static void main(String args[])
    {
        // Custom input data
        int roll[] = { 1, 2, 3, 4 };
        String name[]
            = { "Shubham", "Atul", "Ayush", "Rupesh" };
        int marks[] = { 100, 99, 93, 94 };
        long phone[] = { 8762357381L, 8762357382L,
                         8762357383L, 8762357384L };
        // Creating an object of the class
        GFG custom = new GFG();
        // Now calling function to add the values to the
        // arraylist
        custom.addValues(roll, name, marks, phone);
    }
    public void addValues(int roll[], String name[],
                          int marks[], long phone[])
    {
        // local custom arraylist of data type
        // Data having (int, String, int, long) type
        // from the class
        ArrayList<Data> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            // create an object and send values to the
            // constructor to be saved in the Data class
            list.add(new Data(roll[i], name[i], marks[i],
                              phone[i]));
        }
        // after adding values printing the values to test
        // the custom arraylist
        printValues(list);
    }
    // Method 2
    // To print the values
    public void printValues(ArrayList<Data> list)
    {
        // list- the custom arraylist is sent from
        // previous function
        for (int i = 0; i < n; i++) {
            // Data received from arraylist is of Data type
            // which is custom (int, String, int, long)
            // based on class Data
            Data data = list.get(i);
            // Print and display custom ArrayList elements
            // that holds for student attribute
            // Data variable of type Data has four primitive
            // datatypes roll -int name- String marks- int
            // phone- long
            System.out.println(data.roll + " " + data.name
                               + " " + data.marks + " "
                               + data.phone);
        }
    }
}


1 Shubham 100 8762357381
2 Atul 99 8762357382
3 Ayush 93 8762357383
4 Rupesh 94 8762357384