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POComparing different type of Objects with comparable
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  1. POComparing different type of Objects with comparable
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    copied!<p><code>A.java</code></p> <pre><code>public class A implements Comparable { private String id; private String name; public A(String a, String b) { id = a; name = b; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int compareTo(Object o) { A a = (A) o; return id.compareTo(a.getId()); } } </code></pre> <p><code>B.java</code></p> <pre><code>public class B implements Comparable { private String b_id; private String other; public B(String a, String b) { b_id = a; other = b; } public String getBId() { return b_id; } public void setBId(String id) { this.b_id = id; } public String getOther() { return other; } public void setOther(String other) { this.other = other; } public int compareTo(Object o) { B b = (B) o; return b_id.compareTo(b.getId()); } } </code></pre> <p><code>Learn.java</code></p> <pre><code>public class Learn { public static void main(String[] args) { List&lt;A&gt; listA = new ArrayList&lt;A&gt;(); List&lt;B&gt; listB = new ArrayList&lt;B&gt;(); List&lt;Object&gt; listAll = new ArrayList&lt;Object&gt;(); listA.add(new A("aa", "bb")); listA.add(new A("ae", "bbn")); listA.add(new A("dfr", "GSDS")); listB.add(new B("nm", "re")); listB.add(new B("asd", "asfa")); listAll.addAll(listA); listAll.addAll(listB); Collections.sort(listAll); for (Object o : listAll) { if (o instanceof A) System.out.println(o.getId); else if (o instanceof B) Syatem.out.println(o.getBId); } } } </code></pre> <p>The error i get is at the line <code>Collections.sort(listAll);</code> It says.</p> <pre><code>Bound mismatch: The generic method sort(List&lt;T&gt;) of type Collections is not applicable for the arguments (List&lt;Object&gt;). The inferred type Object is not a valid substitute for the bounded parameter &lt;T extends Comparable&lt;? super T&gt;&gt; </code></pre> <p>What to do? Also is the rest of the logic all right?</p> <p>What i am trying to do is have a list of A and list of B with one attribute same as id; though the variable name is not the same. i.e <code>id</code> in <code>A</code> and <code>bid</code> in B. Now i put both the lists in ListAll and do sort on them on the same variable id/bid. I have A and B implementing Comparable.</p> <p>and my listAll is of type Object?</p> <p>how do I do it? thanks.</p>
 

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