Added state pattern sample

state/src/main/java/com/iluwatar/Mammoth.java

@@ -0,0 +1,32 @@
+package com.iluwatar;
+
+public class Mammoth {
+	
+	private State state;
+
+	public Mammoth() {
+		state = new PeacefulState(this);
+	}
+	
+	public void timePasses() {
+		if (state.getClass().equals(PeacefulState.class)) {
+			changeStateTo(new AngryState(this));
+		} else {
+			changeStateTo(new PeacefulState(this));
+		}
+	}
+
+	private void changeStateTo(State newState) {
+		this.state = newState;
+		this.state.onEnterState();
+	}
+	
+	@Override
+	public String toString() {
+		return "The mammoth";
+	}
+	
+	public void observe() {
+		this.state.observe();
+	}
+}