修改Item且增加4支subclass

Java/src/main/java/com/gildedrose/AgedBrieItem.java

@@ -0,0 +1,20 @@
+package com.gildedrose;
+
+public class AgedBrieItem extends Item {
+
+	public AgedBrieItem(String name, int sellIn, int quality) {
+		super(name, sellIn, quality);
+	}
+
+	@Override
+	public void update() {
+		this.sellIn = this.sellIn - 1;
+
+		this.increaseQuality();
+
+		if (this.sellIn < 0) {
+			this.increaseQuality();
+		}
+	}
+
+}

Java/src/main/java/com/gildedrose/BackstagePassesItem.java

@@ -0,0 +1,28 @@
+package com.gildedrose;
+
+public class BackstagePassesItem extends Item {
+
+	public BackstagePassesItem(String name, int sellIn, int quality) {
+		super(name, sellIn, quality);
+	}
+
+	@Override
+	public void update() {
+		this.sellIn = this.sellIn - 1;
+
+		this.increaseQuality();
+
+		if (this.sellIn < 10) {
+			this.increaseQuality();
+		}
+
+		if (this.sellIn < 5) {
+			this.increaseQuality();
+		}
+
+		if (this.sellIn < 0) {
+			this.quality = this.quality - this.quality;
+		}
+	}
+
+}

Java/src/main/java/com/gildedrose/Item.java

@@ -2,20 +2,36 @@ package com.gildedrose;
 
 public class Item {
 
-    public String name;
+	public String name;
 
-    public int sellIn;
+	public int sellIn;
 
-    public int quality;
+	public int quality;
 
-    public Item(String name, int sellIn, int quality) {
+	public Item(String name, int sellIn, int quality) {
-        this.name = name;
+		this.name = name;
-        this.sellIn = sellIn;
+		this.sellIn = sellIn;
-        this.quality = quality;
+		this.quality = quality;
-    }
+	}
 
-   @Override
+	public void update() {
-   public String toString() {
+
-        return this.name + ", " + this.sellIn + ", " + this.quality;
+	}
-    }
+
+	public void decreaseQuality() {
+		if (this.quality > 0) {
+			this.quality = this.quality - 1;
+		}
+	}
+
+	public void increaseQuality() {
+		if (this.quality < 50) {
+			this.quality = this.quality + 1;
+		}
+	}
+
+	@Override
+	public String toString() {
+		return this.name + ", " + this.sellIn + ", " + this.quality;
+	}
 }

Java/src/main/java/com/gildedrose/NormalItem.java

@@ -0,0 +1,19 @@
+package com.gildedrose;
+
+public class NormalItem extends Item {
+
+	public NormalItem(String name, int sellIn, int quality) {
+		super(name, sellIn, quality);
+	}
+
+	@Override
+	public void update() {
+		this.sellIn = this.sellIn - 1;
+
+		this.decreaseQuality();
+		if (this.sellIn < 0) {
+			this.decreaseQuality();
+		}
+	}
+
+}

Java/src/main/java/com/gildedrose/SulfurasItem.java

@@ -0,0 +1,13 @@
+package com.gildedrose;
+
+public class SulfurasItem extends Item {
+
+	public SulfurasItem(String name, int sellIn, int quality) {
+		super(name, sellIn, quality);
+	}
+
+	@Override
+	public void update() {
+	}
+
+}