Tree in java

 package Trees;

class node{

int val;

node left;

node right;

public node(int val){

    this.val=val;

}

}

public class NodeTree {

public static void main(String[] args) {

node a = new node(1);

node b = new node(4);

node c = new node(3);

node d = new node(2);

node e = new node(6);

node f = new node(5);

a.left=b; a.right=c;

b.left=d; b.right=e;

c.right=f;

System.out.print("product of all nodes : ");

System.out.print(product(a));

System.out.println();

System.out.print("product of non-zero elements of nodes : ");

System.out.print(product2(a));

System.out.println();

System.out.print("sum of all nodes : ");

System.out.print(sum(a));

System.out.println();

System.out.print("Maximum Node in tree : ");

System.out.print(maximum(a));

System.out.println();

System.out.print("Minimum Node in tree : ");

System.out.print(minimum(a));

System.out.println();

System.out.print("size of tree : ");

System.out.print(size(a));

System.out.println();

System.out.print("total levels in tree : ");

System.out.print(level(a));

System.out.println();

System.out.print("Height of tree : ");

System.out.print(level(a)-1);

System.out.println();

//three types of traversal-

System.out.print("preorder : ");

preorder(a);

System.out.println();

System.out.print("inorder : ");

inorder(a);

System.out.println();

System.out.print("postorder : ");

postorder(a);

}

public static int level(node root){

    if(root==null) return 0;

    return 1 + Math.max(level(root.left),level(root.right));

}

public static int size(node root){

    if(root==null) return 0;

    return 1 + size(root.left)+size(root.right);

}

public static int minimum(node root){

if(root==null) return Integer.MAX_VALUE;

return Math.min(root.val, Math.min(minimum(root.left),minimum(root.right)));

}

public static int maximum(node root){

if(root==null) return Integer.MIN_VALUE;

return Math.max(root.val, Math.max(maximum(root.left),maximum(root.right)));

}

public static int product2(node root){

    if(root==null) return 1;

    if(root.val==0)

    return product2(root.left) * product2(root.right);

    return root.val * product2(root.left) * product2(root.right);

}

public static int product(node root){

    if(root==null) return 1;

    return root.val * product(root.left) * product(root.right);

}

public static int sum(node root){

    if(root==null) return 0;

    return root.val + sum(root.left) + sum(root.right);

}

public static void preorder(node root){

if(root==null) return;

System.out.print(root.val+" ");

preorder(root.left);

preorder(root.right);

}

public static void inorder(node root){

if(root==null) return;

inorder(root.left);

System.out.print(root.val+" ");

inorder(root.right);

}

public static void postorder(node root){

if(root==null) return;

postorder(root.left);

postorder(root.right);

System.out.print(root.val+" ");

}

}