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This article introduces the relevant knowledge of "what are the ways to solve the trouble of writing if else". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

If else is one of the most frequently used keywords when we write code, but sometimes too much if else can make us feel pain in the skull.

For example, the following pseudo code:

Is it freaking out? Although it is pseudocode and looks exaggerated, in reality, we will find a similar scenario when we Review other people's code countless times.

Here are nine ways to get rid of those "annoying" if else. Let's take a look.

1. Use return

We use return to remove the excess else, and the implementation code is as follows.

Pre-optimization code:

If ("java" .equals (str)) {/ / business code. } else {return;}

Optimized code:

If (! "java" .equals (str)) {return;} / / business code.

This will look much more comfortable, although the difference is only one line of code, but the gap between real experts and ordinary people is reflected in this line of code.

"Don't give up doing good, even if it's not important, don't do bad things, even if it's inconspicuous."A dike of a thousand miles is broken in an ant's nest." it's the same truth.

two。 Use Map

Using the Map array, defining the relevant judgment information as element information can directly avoid if else judgment. The implementation code is as follows.

Pre-optimization code:

If (t = = 1) {type = "name";} else if (t = = 2) {type = "id";} else if (t = = 3) {type = "mobile";}

Let's first define a Map array to store the relevant judgment information:

Map typeMap = new HashMap (); typeMap.put (1, "name"); typeMap.put (2, "id"); typeMap.put (3, "mobile")

The previous judgment statement can be replaced with the following line of code:

Type = typeMap.get (t)

3. Use ternary operators

Ternary operators are also called ternary expressions or ternary operators / expressions, but they all mean the same thing, and the optimization code is as follows.

Pre-optimization code:

Integer score = 81; if (score > 80) {score = 100;} else {score = 60;}

Optimized code:

Score = score > 80? 100: 60

4. Merge conditional expression

There are some logical judgments in the project that can be combed and summarized and changed into easier-to-understand logical judgment code, as shown below.

Pre-optimization code:

String city = "Xi'an"; String area = "029"; String province = "Shaanxi"; if ("Xi'an" .equals (city)) {return "xi'an";} if ("029.equals (area)) {return" xi'an ";} if (" Shaanxi ".equals (province)) {return" xi'an ";}

Optimized code:

If ("Xi'an" .equals (city) | | "029.equals (area) | |" Shaanxi ".equals (province)) {return" xi'an ";}

5. Use enumerations

A new type, enum, has been introduced in JDK 1.5, which we can use to accomplish many functions, such as the following one.

Pre-optimization code:

Integer typeId = 0; String type = "Name"; if ("Name" .equals (type)) {typeId = 1;} else if ("Age" .equals (type)) {typeId = 2;} else if ("Address" .equals (type)) {typeId = 3;}

When optimizing, let's first define an enumeration:

Public enum TypeEnum {Name (1), Age (2), Address (3); public Integer typeId; TypeEnum (Integer typeId) {this.typeId = typeId;}}

The previous if else judgment can be replaced by the following line of code:

TypeId = TypeEnum.valueOf ("Name") .typeId

6. Use Optional

The Optional class has been introduced since JDK 1.8, and the Optional class has been improved in JDK 9 with the addition of the ifPresentOrElse () method, which we can use to eliminate if else judgment, using the following.

Pre-optimization code:

String str = "java"; if (str = = null) {System.out.println ("Null");} else {System.out.println (str);}

Optimized code:

Optional opt = Optional.of ("java"); opt.ifPresentOrElse (v-> System.out.println (v), ()-> System.out.println ("Null"))

Tip: pay attention to running the version, it must be JDK 9 +.

7. Combing the logic of optimizing judgment

Similar to point 4, we can write more understandable code by analyzing the logical judgment semantics of if else, such as the following optimization of nested judgment.

Pre-optimization code:

/ / Age > 18 if (age > 18) {/ / salary > 5000 if (salary > 5000) {/ / pretty if (pretty = = true) {return true;} return false

Optimized code:

If (age

< 18) { return false; } if (salary < 5000) { return false; } return pretty; 我们需要尽量把表达式中的包含关系改为平行关系，这样代码可读性更高，逻辑更清晰。 8.使用多态 继承、封装和多态是 OOP(面向对象编程)的重要思想，本文我们使用多态的思想，提供一种去除 if else 方法。 优化前代码： Integer typeId = 0; String type = "Name"; if ("Name".equals(type)) { typeId = 1; } else if ("Age".equals(type)) { typeId = 2; } else if ("Address".equals(type)) { typeId = 3; } 使用多态，我们先定义一个接口，在接口中声明一个公共返回 typeId 的方法，在添加三个子类分别实现这三个子类。 实现代码如下： public interface IType { public Integer getType(); } public class Name implements IType { @Override public Integer getType() { return 1; } } public class Age implements IType { @Override public Integer getType() { return 2; } } public class Address implements IType { @Override public Integer getType() { return 3; } } 注意：为了简便我们这里把类和接口放到了一个代码块中，在实际开发中应该分别创建一个接口和三个类分别存储。 此时，我们之前的 if else 判断就可以改为如下代码： IType itype = (IType) Class.forName("com.example." + type).newInstance(); Integer typeId = itype.getType(); 有人可能会说，这样反而让代码更加复杂了，此可谓"杀鸡焉用宰牛刀"的典型范例了。 这里作者只是提供一种实现思路和提供了一些简易版的代码，以供开发者在实际开发中，多一种思路和选择，具体用不用需要根据实际情况来定了。灵活变通，举一反三，才是开发的上乘心法。 9.选择性的使用 switch 很多人都搞不懂 switch 和 if else 的使用场景，但在两者都能使用的情况下，可以尽量使用 switch，因为 switch 在常量分支选择时，switch 性能会比 if else 高。 if else 判断代码： if ("add".equals(cmd)) { result = n1 + n2; } else if ("subtract".equals(cmd)) { result = n1 - n2; } else if ("multiply".equals(cmd)) { result = n1 * n2; } else if ("divide".equals(cmd)) { result = n1 / n2; } else if ("modulo".equals(cmd)) { result = n1 % n2; } switch 代码： switch (cmd) { case "add": result = n1 + n2; break; case "subtract": result = n1 - n2; break; case "multiply": result = n1 * n2; break; case "divide": result = n1 / n2; break; case "modulo": result = n1 % n2; break; } 在 Java 14 可使用 switch 代码块，实现代码如下： // java 14 switch (cmd) { case "add" ->

{result = N1 + N2;} case "subtract"-> {result = N1-N2;} case "multiply"-> {result = N1 * N2;} case "divide"-> {result = N1 / N2;} case "modulo"-> {result = N1% N2 This is the end of the content of "what are the ways to solve the trouble of writing if else". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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