Add snipet chpt 4

snippet/ch4/Account.java

+public class Account {
+
+  private final String owner;
+  private double balance;
+
+  public Account(String owner, double balance) {
+    this.owner = owner;
+    this.balance = balance;
+  }
+
+  public Account(String owner) { 
+    this(owner, 0.0); 
+  }
+
+  public String getOwner() { return this.owner; }
+  public double getBalance() { return this.balance; }
+
+  public void deposite(double amount) { this.balance += amount; }
+  public void withdraw(double amount) { this.deposite(-amount); }
+
+}