Using Strategy Enum to Replace Large if‑else Chains in Java

The author reflects on early Java OOP programming where many if‑else statements cluttered code, noting that excessive if‑else is a procedural implementation.

When a business requires handling a week’s worth of daily tasks, a long if‑else chain becomes unreadable and redundant.

To solve this, the author recommends using a strategy enum, which offers better readability, extensibility, and a lightweight alternative to factories, classic strategy pattern, or heavy rule engines.

Traditional if‑else implementation for a getToDo(String day) method:

<code style="padding: 16px; color: black; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px"> <span style="color: #1c00cf; line-height: 26px">1</span> <span style="color: #007400; line-height: 26px">//if-else形式判断</span><br/> <span style="color: #1c00cf; line-height: 26px">2</span> <span style="line-height: 26px"><span style="color: #aa0d91; line-height: 26px">public</span> String <span style="color: #1c00cf; line-height: 26px">getToDo</span><span style="color: #5c2699; line-height: 26px">(String day)</span></span>{<br/> <span style="color: #1c00cf; line-height: 26px">3</span>     <span style="color: #aa0d91; line-height: 26px">if</span>(<span style="color: #c41a16; line-height: 26px">"Monday"</span>.equals(day)){<br/>          ......省略复杂语句<br/> <span style="color: #1c00cf; line-height: 26px">4</span>         <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上英语课"</span>;<br/> <span style="color: #1c00cf; line-height: 26px">5</span>     }<span style="color: #aa0d91; line-height: 26px">else</span> <span style="color: #aa0d91; line-height: 26px">if</span>(<span style="color: #c41a16; line-height: 26px">"Tuesday"</span>.equals(day)){<br/>          .....省略复杂语句<br/>          <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上语文课"</span>;<br/> <span style="color: #1c00cf; line-height: 26px">7</span>     }<span style="color: #aa0d91; line-height: 26px">else</span> <span style="color: #aa0d91; line-height: 26px">if</span>(<span style="color: #c41a16; line-height: 26px">"Wednesday"</span>.equals(day)){<br/>         ......省略复杂语句<br/> <span style="color: #1c00cf; line-height: 26px">8</span>         <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上数学课"</span>;<br/> <span style="color: #1c00cf; line-height: 26px">9</span>     }<span style="color: #aa0d91; line-height: 26px">else</span> <span style="color: #aa0d91; line-height: 26px">if</span>(<span style="color: #c41a16; line-height: 26px">"Thursday"</span>.equals(day)){<br/>         ......省略复杂语句<br/><span style="color: #1c00cf; line-height: 26px">10</span>         <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上音乐课"</span>;<br/><span style="color: #1c00cf; line-height: 26px">11</span>     }<span style="color: #aa0d91; line-height: 26px">else</span> <span style="color: #aa0d91; line-height: 26px">if</span>(<span style="color: #c41a16; line-height: 26px">"sunday"</span>.equals(day)){<br/>         ......省略复杂语句<br/><span style="color: #1c00cf; line-height: 26px">12</span>         <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上编程课"</span>;<br/><span style="color: #1c00cf; line-height: 26px">13</span>     }<span style="color: #aa0d91; line-height: 26px">else</span>{<br/><span style="color: #1c00cf; line-height: 26px">14</span>         此处省略<span style="color: #1c00cf; line-height: 26px">10086</span>行......<br/><span style="color: #1c00cf; line-height: 26px">15</span>     }<br/><span style="color: #1c00cf; line-height: 26px">16</span> }<br/></code>

This code works for a few cases, but when hundreds of branches are needed it becomes unwieldy.

The refactored approach defines a getToDo method that delegates to a CheckDay class, which calls DayEnum.valueOf(day) and then invokes the enum’s toDo() method.

<code style="padding: 16px; color: black; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px"><span style="color: #007400; line-height: 26px">//策略枚举判断</span><br/><span style="line-height: 26px"><span style="color: #aa0d91; line-height: 26px">public</span> String <span style="color: #1c00cf; line-height: 26px">getToDo</span><span style="color: #5c2699; line-height: 26px">(String day)</span></span>{<br/>    CheckDay checkDay=<span style="color: #aa0d91; line-height: 26px">new</span> CheckDay();<br/>    <span style="color: #aa0d91; line-height: 26px">return</span> checkDay.day(DayEnum.valueOf(day));<br/>}<br/></code>

Inside CheckDay.day(DayEnum dayEnum) the call simply returns dayEnum.toDo(), delegating the actual work to the enum constant.

<code style="padding: 16px; color: black; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px"><span style="color: #aa0d91; line-height: 26px">public</span> <span style="color: #aa0d91; line-height: 26px">class</span> CheckDay {<br/>    <span style="color: #aa0d91; line-height: 26px">public</span> <span style="color: #5c2699; line-height: 26px">String</span> day( DayEnum dayEnum) {<br/>        <span style="color: #aa0d91; line-height: 26px">return</span> dayEnum.toDo();<br/>    }<br/>}<br/></code>

The DayEnum enum declares an abstract toDo() method and overrides it in each constant (Monday, Tuesday, …), allowing each day to return its specific task string.

<code style="padding: 16px; color: black; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px"><span style="color: #aa0d91; line-height: 26px">public</span> <span style="color: #aa0d91; line-height: 26px">enum</span> DayEnum {<br/>    Monday {<br/>        <span style="color: #643820; line-height: 26px">@Override</span><br/>        <span style="line-height: 26px"><span style="color: #aa0d91; line-height: 26px">public</span> String <span style="color: #1c00cf; line-height: 26px">toDo</span><span style="color: #5c2699; line-height: 26px">()</span> </span>{<br/>            ......省略复杂语句<br/>            <span style="color: #aa0d91; line-height: 26px">return</span> <span style="color: #c41a16; line-height: 26px">"今天上英语课"</span>;<br/>        }<br/>    },<br/>    Tuesday {…},<br/>    Wednesday {…},<br/>    Thursday {…};<br/>    <span style="line-height: 26px"><span style="color: #aa0d91; line-height: 26px">public</span> <span style="color: #aa0d91; line-height: 26px">abstract</span> String <span style="color: #1c00cf; line-height: 26px">toDo</span><span style="color: #5c2699; line-height: 26px">()</span></span>;<br/>}<br/></code>

To handle duplicate functionality (e.g., several days sharing the same task), an internal enum Type is introduced; each day stores a Type and delegates its toDo() to the shared implementation.

<code style="padding: 16px; color: black; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px"><span style="color: #aa0d91; line-height: 26px">public</span> <span style="color: #aa0d91; line-height: 26px">enum</span> DayEnum {<br/>    Monday(<span style="color: #c41a16; line-height: 26px">"星期一"</span>, Type.ENGLISH),<br/>    Tuesday(<span style="color: #c41a16; line-height: 26px">"星期二"</span>, Type.ENGLISH),<br/>    Wednesday(<span style="color: #c41a16; line-height: 26px">"星期三"</span>, Type.ENGLISH),<br/>    Thursday(<span style="color: #c41a16; line-height: 26px">"星期四"</span>, Type.CHINESE);<br/>    private final Type type;<br/>    private final String day;<br/>    DayEnum(String day, Type type) {<br/>        this.day = day;<br/>        this.type = type;<br/>    }<br/>    String toDo() {<br/>        return type.toDo();<br/>    }<br/>    private enum Type {<br/>        ENGLISH {<br/>            @Override<br/>            public String toDo() {<br/>                ......省略复杂语句<br/>                return "今天上英语课";<br/>            }<br/>        },<br/>        CHINESE {<br/>            @Override<br/>            public String toDo() {<br/>                ......省略复杂语句<br/>                return "今天上语文课";<br/>            }<br/>        };<br/>        public abstract String toDo();<br/>    }<br/>}<br/></code>

The author concludes that strategy enums combine the strategy pattern with enums, offering a functional‑style solution that decouples complex branching logic, improves maintainability, and behaves like a key‑to‑door mechanism.

At the end, the author promotes his PDF collections on Spring Cloud, Spring Boot, and MyBatis, and asks readers to like, share, and follow his public account.