class codingQuestion3 {

public static void concat1(String s1) {
s1 = s1 + "test1";
}

public static void concat2(StringBuilder s2) {
s2.append("test2");
}

public static void concat3(StringBuffer s3) {
s3.append("test3");
}

public static void main(String[] args) {

String s1 = "test1";
concat1(s1);  test1test1
System.out.println("String: " + s1);
StringBuilder s2 = new StringBuilder("test2");
concat2(s2); test2test2
System.out.println("StringBuilder: " + s2);
StringBuffer s3 = new StringBuffer("test3");
concat3(s3);
System.out.println("StringBuffer: " + s3);
}
}


abstract class Bank {
abstract int getRateOfInterest();
}

class SBI extends Bank {
int getRateOfInterest() {
return 7;
}

void test() {
System.out.println("test called");
}
}

class PNB extends Bank {
int getRateOfInterest() {
return 8;
}
}

class TestBank {
public static void main(String args[]) {
Bank b = new SBI();
b.test(); 
SBI k = new SBI();
k.test(); test called
int interest = b.getRateOfInterest();
System.out.println("Rate of Interest is: " + interest + " %");
}
}




class P {
static void ab() {
System.out.println("P");
}
}

class A extends P {
static void ab() {
System.out.println("a");
}
}

class B extends P {
static void ab() {
System.out.println("b");
}

public static void main(String ar[]) {
P p = new A();
A a = new A();
p.ab();
p = new B();
p.ab();
a.ab();
}




						10

				 6				4
		3			3		2		2




Public boolean isSumTree(TreeNode root)
{
	return helper(root);

}

Public boolean helper(TreeNode root)
{
	if(root == null)
 		return true;
	if(root.left == null && root.right == null)
		return true;
	int sum = root.left == null?0:root.left.data + root.right == null?0:root.data;
	if(sum != root.data)
		return false;

	return helper(root.left) && helper(root.right);

}