ジェネリック型から文字列を返す方法

Question

返り値は型文字列なので返すことはできませんが、文字列変数を適用して結果を渡すことはできません。文字列としての私のwhileループの結果？私は明らかに動作しない文字列変数を適用しようとした後、文字列変数を作成し、それらをroot.inorderのものに連結しますが、それはオペランド+のために動作しません。ただroot.inorder(iter)戻りTを想定し

public String toString() { 

    ArrayIterator<T> iter = new ArrayIterator<T>(); 

    String result = ""; 

    while (iter.hasNext()) 
     result += root.inorder(iter).toString(); 

    return result;   
} 

を行うと間違って何

public String toString() { 

    ArrayIterator<T> iter = new ArrayIterator<T>(); 

    String result = ""; 

    while (iter.hasNext()) 
     root.inorder(iter); 

    return null;   
} 

package javafoundations; 


public class Project10 { 

private static LinkedBinaryTree<Integer> tree; 

    public static void main (String[] args) { 

     LinkedBinaryTree<Integer> n2, n3, n4, n5, n6, n7, n8 ,n9, n10, n11, n12, n13; 

     Integer e1 = 10; 
     Integer e2 = 6; 
     Integer e3 = 19; 
     Integer e4 = 4; 
     Integer e5 = 8; 
     Integer e6 = 16; 
     Integer e7 = 20; 
     Integer e8 = 3; 
     Integer e9 = 5; 
     Integer e10 = 7; 
     Integer e11 = 9; 
     Integer e12 = 15; 
     Integer e13 = 17; 

     n8 = new LinkedBinaryTree<Integer>(e8); 
     n9 = new LinkedBinaryTree<Integer>(e9); 
     n4 = new LinkedBinaryTree<Integer>(e4, n8, n9); 

     n10 = new LinkedBinaryTree<Integer>(e10); 
     n11 = new LinkedBinaryTree<Integer>(e11); 
     n5 = new LinkedBinaryTree<Integer>(e5, n10, n11); 

     n12 = new LinkedBinaryTree<Integer>(e12); 
     n13 = new LinkedBinaryTree<Integer>(e13); 
     n6 = new LinkedBinaryTree<Integer>(e6, n12, n13); 

     n7 = new LinkedBinaryTree<Integer>(e7); 

     n3 = new LinkedBinaryTree<Integer>(e3, n6, n7); 
     n2 = new LinkedBinaryTree<Integer>(e2, n4, n5); 

     tree = new LinkedBinaryTree<Integer>(e1, n2, n3); 

     System.out.println("find: " + tree.find(e13)); 
     System.out.println("Contains: " + tree.contains(e1)); 
     System.out.println("empty?: " + tree.isEmpty()); 
     System.out.println("size: " + tree.size()); 
     System.out.println("getRoot: " + tree.getRootElement()); 

     System.out.println(tree); 
     System.out.println(tree.getLeft()); 
     System.out.println(tree.getLeft().toString()); 
     System.out.println(tree.levelorder()); 
     System.out.println(tree.inorder()); 
     System.out.println(tree.preorder()); 
     System.out.println(tree.postorder()); 




     /*StudentRecord<String, String> student1 = new StudentRecord<String, String>("Mike Litoris", 1235, "Sophomore \n"); 
     StudentRecord<String, String> student2 = new StudentRecord<String, String>("Graham Swallows", 1236, "Freshman\n"); 
     StudentRecord<String, String> student3 = new StudentRecord<String, String>("Gift Sales", 1237, "Senior\n"); 
     StudentRecord<String, String> student4 = new StudentRecord<String, String>("Chew Kok", 1238, "Junior\n"); 
     StudentRecord<String, String> student5 = new StudentRecord<String, String>("Bob Dylan", 5678, "Senior\n"); 

     BTNode<StudentRecord<String, String>> student = new BTNode<StudentRecord<String, String>>(student1); 


     student.setLeft(student1);*/ 

    } 
} 

Answer 1

。