Build A Generic Tree With Inheritance

Question

I am building a generic Tree class, which supports inheritance of sub-trees. But I\'ve encountered some problems. Would you please kindly help me?

Answer 1

did you try such code?

package trees;                                                                                                          

import java.util.ArrayList;                                                                                             

public class Trees {                                                                                                    

    public static void main(String... args) {                                                                           
        Tree> tree_leaf = new Tree<>();                                                   
        BlueTree> blueTree_leaf = new BlueTree<>();                                   
        Tree> tree_redLeaf = new Tree<>();                                          
        BlueTree> blueTree_redLeaf = new BlueTree<>();                          
        //1                                                                                                             
        tree_leaf.addChild(tree_leaf);                                                                                  
        tree_leaf.addChild(tree_redLeaf);                                                                               
        tree_leaf.addChild(blueTree_leaf);                                                                              
        tree_leaf.addChild(blueTree_redLeaf);                                                                           
        //2                                                                                                             
        tree_redLeaf.addChild(tree_redLeaf);                                                                            
        tree_redLeaf.addChild(blueTree_redLeaf);                                                                        
        tree_redLeaf.addChild(tree_leaf);//compile error                                                                
        tree_redLeaf.addChild(blueTree_leaf);//compile error                                                            
        //3                                                                                                             
        blueTree_leaf.addChild(blueTree_leaf);                                                                          
        blueTree_leaf.addChild(blueTree_redLeaf);                                                                       
        blueTree_leaf.addChild(tree_leaf);//compile error                                                               
        blueTree_leaf.addChild(tree_redLeaf);//compile error                                                            
        //4                                                                                                             
        blueTree_redLeaf.addChild(blueTree_redLeaf);                                                                    
        blueTree_redLeaf.addChild(tree_leaf);//compile error                                                            
        blueTree_redLeaf.addChild(tree_redLeaf);//compile error                                                         
        blueTree_redLeaf.addChild(blueTree_leaf);//compile error                                                        

    }                                                                                                                   
}                                                                                                                       

class Tree> {                                                            

    //important in this question                                                                                        
    private Tree mParent;                                                               
    private Data mData;                                                                                                 
    private ArrayList mChildren;                                                                              

    // This is the focus of this question, the addChild() method signature                                              
    public void addChild(final Children subTree) {                                                                      
        // add the subTree to mChildren                                                                                 
    }                                                                                                                   

}                                                                                                                       


class BlueTree> extends Tree {                       
}                                                                                                                       

class Leaf {                                                                                                            
}                                                                                                                       

class RedLeaf extends Leaf {                                                                                            
}