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

## Java Basic: Exercise-127 with Solution

Write a Java program to get the Postorder traversal of its nodes' values of a given a binary tree.

Sample Binary Tree Postorder 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_Postorder(Node node)
{
if (node == null)
return;

print_Postorder(node.left);

print_Postorder(node.right);

System.out.print(node.key + " ");
}

// Wrappers over above recursive functions
void print_Postorder()
{
print_Postorder(root);
}
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("\nPostorder traversal of binary tree is: ");
tree.print_Postorder();
}
}
```
```

Sample Output:

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

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