Question

How to create a generic array in Java

Answer 1

import java.util.Arrays;
 
class Array<T>
{
    private final Object[] arr;
    public final int length;
 
    public Array(int length) {
        arr = new Object[length];
        this.length = length;
    }
 
    void set(int i, T val) {
        arr[i] = val;
    }
 
    public String toString() {
        return Arrays.toString(arr);
    }
}
 
public class MyClass
{
    public static void main(String[] args)
    {
        final int length = 7;
 
        Array<Integer> intArray = new Array(length);
 
        for (int i = 0; i < length; i++) {
            intArray.set(i, i + 1);
        }
 
        System.out.println(intArray);
 
        Array<String> strArray = new Array(length);
 
        for (int i = 0; i < length; i++) {
            strArray.set(i, String.valueOf((char)(i + 65)));
        }
 
        System.out.println(strArray);
    }
}
 
 
 
 
 
/*
run:
  
[1, 2, 3, 4, 5, 6, 7]
[A, B, C, D, E, F, G]
  
*/

 

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Answer 2

import java.util.Arrays;
 
class Array<T>
{
    private final Object[] arr;
    public final int length;
 
    public Array(int length) {
        arr = new Object[length];
        this.length = length;
    }
 
    T get(int i) {
        final T e = (T)arr[i];
        return e;
    }
 
    void set(int i, T val) {
        arr[i] = val;
    }
 
    public String toString() {
        return Arrays.toString(arr);
    }
}
 
public class MyClass
{
    public static void main(String[] args)
    {
        final int length = 7;
 
        Array<Integer> intArray = new Array(length);
 
        for (int i = 0; i < length; i++) {
            intArray.set(i, i + 1);
        }
 
        System.out.println(intArray.get(1));
        System.out.println(intArray.get(3));
 
        Array<String> strArray = new Array(length);
 
        for (int i = 0; i < length; i++) {
            strArray.set(i, String.valueOf((char)(i + 65)));
        }
 
        System.out.println(strArray.get(1));
        System.out.println(strArray.get(3));
    }
}
 
 
 
 
 
/*
run:
  
2
4
B
D
  
*/

 

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