Added state pattern sample

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

@@ -0,0 +1,21 @@
+package com.iluwatar;
+
+public class PeacefulState implements State {
+	
+	private Mammoth mammoth;
+
+	public PeacefulState(Mammoth mammoth) {
+		this.mammoth = mammoth;
+	}
+
+	@Override
+	public void observe() {
+		System.out.println(String.format("%s is calm and peaceful.", mammoth));
+	}
+
+	@Override
+	public void onEnterState() {
+		System.out.println(String.format("%s calms down.", mammoth));
+	}
+	
+}