How to use Guava function library to simplify programming in Java

With the continuous development of the Java language, developers have increasingly higher requirements for programming efficiency and code readability. This brings up the question of how to use Java function libraries to improve programming efficiency and code readability. Among them, Guava is an excellent Java function library that provides many powerful functions and tool classes to simplify Java programming.

1. Introducing the Guava function library

To use the Guava function library in Java, you need to download the corresponding jar package first and introduce it into the project. The download address of the Guava function library is: https://github.com/google/guava/releases. After the download is completed, the steps to introduce it into the project are as follows:

(1) Copy the downloaded jar package to the project lib directory.

(2) In Eclipse, right-click the project -> Build Path -> Configure Build Path -> Libraries -> Add JARS, and select the jar package you just copied.

(3) In the Maven project, add the following dependencies in pom.xml:

<dependency> 
   <groupId>com.google.guava</groupId> 
   <artifactId>guava</artifactId> 
   <version>28.0-jre</version> 
</dependency> 

2. Commonly used functions and tool classes in Guava

(1) Strings

In Java, there may be many tedious operations when processing strings, and the Strings class in Guava provides a wealth of string tool methods.

For example:

String str = "hello";
System.out.println(Strings.isNullOrEmpty(str)); // 判断字符串是否为空或null
System.out.println(Strings.padStart(str, 10, ' ')); // 左侧填充空格
System.out.println(Strings.padEnd(str, 10, ' ')); // 右侧填充空格

(2) CharMatcher

The CharMatcher class is a tool class used to handle character matching.

For example:

String str = "hello world!";
System.out.println(CharMatcher.is('l').countIn(str)); // 统计字符串中l的数量
System.out.println(CharMatcher.anyOf("aeiou").removeFrom(str)); // 移除字符串中的元音字母
System.out.println(CharMatcher.inRange('a', 'm').retainFrom(str)); // 只保留字符串中a-m之间的字母

(3) Joiner

In Java, splicing strings may be a troublesome thing, and the Joiner class in Guava provides a Very convenient method.

For example:

List<String> list = Lists.newArrayList("hello", "world");
System.out.println(Joiner.on(",").join(list)); // 将列表中的元素用逗号连接起来

(4) Splitter

The Splitter class is a separator tool class that is responsible for splitting a string into substrings.

For example:

String str = "hello,world";
List<String> list = Splitter.on(",").splitToList(str); // 将字符串拆分成列表
System.out.println(list); // 输出：[hello, world]

(5) Optional

The Optional class is a method provided in Guava to handle values ​​that may be empty.

For example:

String str = "hello";
Optional<String> optional = Optional.ofNullable(str);
System.out.println(optional.isPresent()); // 判断optional是否有值
System.out.println(optional.orElse("world")); // 如果optional没有值，则返回默认值

(6) Preconditions

The Preconditions class provides some precondition checking methods. Adding assertions to the code can improve the readability and readability of the code. Maintainability.

For example:

public void test(String str) {
    Preconditions.checkNotNull(str, "str参数不能为空");
    // 其他代码
}

3. Summary

In Java development, the Guava function library provides us with many convenient functions and tool classes, simplifying Java programming. We only need to be proficient in its use to greatly improve the efficiency and readability of our code.

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