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    <p>Inheritance gives you common API and common base type not the data.</p> <p>Add copy constructor which takes "A" argument and then copy properties from passed "A" object. Something like this:</p> <pre><code>package com.example; import java.io.IOException; import java.util.Scanner; class A { int a[]; int no; A() { } void init() { System.out.println("Number of elements for an array : "); Scanner in1 = new Scanner(System.in); no = in1.nextInt(); a = new int[no]; for (int i = 0; i &lt; no; i++) { System.out.println("Enter elements : "); Scanner in2 = new Scanner(System.in); a[i] = in2.nextInt(); } } void sort() { int tmp; for (int i = 0; i &lt; no - 1; i++) { for (int j = i + 1; j &lt; no; j++) { System.out.println("a[i] : " + a[i] + " a[i+1] : " + a[i + 1]); if (a[i] &gt; a[j]) { tmp = a[i]; a[i] = a[j]; a[j] = tmp; } } } } void display() { System.out.println(); for (int i = 0; i &lt; no; i++) { System.out.println(a[i]); } } } class B extends A { B(A obj) { no = obj.no; a = new int[obj.a.length]; System.arraycopy( obj.a, 0, a, 0, obj.a.length ); } int tot = 0; float mean; void get_mean() { System.out.println("no : " + no); for (int i = 0; i &lt; no; i++) { tot += a[i]; } System.out.println("tot : " + tot); mean = (float) tot / no; System.out.println("mean : " + mean); } } class C extends A { C(A obj) { no = obj.no; a = new int[obj.a.length]; System.arraycopy( obj.a, 0, a, 0, obj.a.length ); } void median() { float median; if (no % 2 == 0) { int middle = no / 2; median = ((a[middle] + a[middle / 2]) / 2); } else { median = a[(no / 2)]; } System.out.println("median : " + median); } } public class Test { public static void main(String arg[]) throws IOException { A objA = new A(); objA.init(); B obj1 = new B(objA); obj1.get_mean(); C obj2 = new C(objA); obj2.sort(); obj2.median(); } } </code></pre> <p>But better approach is to use composition rather than inheritance. Just let your A class collect data and then inject this "data" object to B, C. B and C dont need to be "IS-A" objects. They should be "HAS-A" objects.</p>
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