﻿ Java exercises: Get the preorder traversal of its nodes' values of a given a binary tree - w3resource # Java Exercises: Get the preorder traversal of its nodes' values of a given a binary tree.

## Java Basic: Exercise-125 with Solution

Write a Java program to get the preorder traversal of its nodes' values of a given a binary tree.
Example:
Expected output: 10 20 40 50 30

Sample Binary Tree Preorder Traversal: Sample Solution:

Java Code:

``````class Node
{
int key;
Node left, right;

public Node(int item)
{
key = item;
left = right = null;
}
}

class BinaryTree
{
// Root of Binary Tree
Node root;
BinaryTree()
{
root = null;
}

// Print the nodes of binary tree

void print_Preorder(Node node)
{
if (node == null)
return;

/* Print data of node */
System.out.print(node.key + " ");

print_Preorder(node.left);

print_Preorder(node.right);
}

void print_Preorder()
{
print_Preorder(root);
}

// Driver method
public static void main(String[] args)
{
BinaryTree tree = new BinaryTree();
tree.root = new Node(55);
tree.root.left = new Node(21);
tree.root.right = new Node(80);
tree.root.left.left = new Node(9);
tree.root.left.right = new Node(29);
tree.root.right.left = new Node(76);
tree.root.right.right = new Node(91);

System.out.println("Preorder traversal of binary tree is: ");
tree.print_Preorder();
}
}
```
```

Sample Output:

```Preorder traversal of binary tree is:
55 21 9 29 80 76 91
```

Flowchart: Java Code Editor:

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## Java: Tips of the Day

Try and catch:

Java is excellent at catching errors, but it can only recover gracefully if you tell it what to do. The cascading hierarchy of attempting to perform an action in Java starts with try, falls back to catch, and ends with finally. Should the try clause fail, then catch is invoked, and in the end, there's always finally to perform some sensible action regardless of the results. Here's an example:

```try {
cmd = parser.parse(opt, args);

if(cmd.hasOption("help")) {
HelpFormatter helper = new HelpFormatter();
helper.printHelp("Hello ", opt);
System.exit(0);
}
else {
if(cmd.hasOption("shell") || cmd.hasOption("s")) {
String target = cmd.getOptionValue("tgt");
} // else
} // fi
} catch (ParseException err) {
System.out.println(err);
System.exit(1);
} //catch
finally {
new Hello().helloWorld(opt);
} //finally
} //try
```

It's a robust system that attempts to avoid irrecoverable errors or, at least, to provide you with the option to give useful feedback to the user. Use it often, and your users will thank you!

Ref: https://red.ht/3EZc9OC