Java String replaceAll() replaces all the occurrences of a particular character, string or a regular expression in the string. The method returns a new string as its output. The method requires two parameters.

Java字符串replaceAll（）替换所有出现的特定字符，字符串或字符串中的正则表达式。 该方法返回一个新字符串作为其输出。 该方法需要两个参数。

字符串replaceAll（）语法 (String replaceAll() Syntax)

public String replaceAll(String regex, String replacement)

A regex that represents the pattern to look for while replacing and a replacement string to replace it with.

一个正则表达式 ，代表替换时要查找的模式以及替换 字符串 。

There are multiple types of substitutions that are possible with String replaceAll() method.

字符串replaceAll（）方法可能有多种替换类型。

替换单个字符 (Replacing a single character )

To replace a single character, specify the character to be replaced as the regex.

要替换单个字符，请指定要替换的字符作为正则表达式。

public class Main {public static void main(String[] args) {String s = "Welcome to JournalDev";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceAll("o","@");System.out.println("New String: "+rep);}
}

Original String: Welcome to JournalDevNew String: Welc@me t@ J@urnalDev

替换字符序列 (Replace sequence of characters )

To replace a sequence of characters, mention the sequence as the regex in the replaceAll() function.

要替换字符序列，请在replaceAll（）函数中将该序列称为正则表达式。

public class Main {public static void main(String[] args) {String s = "Welcome to JournalDev";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceAll("to","this is");System.out.println("New String: "+rep);}
}

Original String : Welcome to JournalDevNew String: Welcome this is JournalDev

删除/替换空间 (Remove/Replace Spaces)

The replaceAll() method can remove or replace the whitespaces in your text string.

replaceAll（）方法可以删除或替换文本字符串中的空格。

public class Main {public static void main(String[] args) {String s = "Welcome to JournalDev";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceAll(" ","");System.out.println("New String: "+rep);}
}

Original String : Welcome to JournalDevNew String: WelcometoJournalDev

Similarly, to replace the whitespaces:

同样，要替换空白：

public class Main {public static void main(String[] args) {String s = "Welcome to JournalDev";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceAll(" ","_");System.out.println("New String: "+rep);}
}

Original String : Welcome to JournalDevNew String: Welcome_to_JournalDev

隐藏文本中的数字 (Hiding numeric digits in a text )

The replaceAll() can hide numeric digits that appear in a string. The digits can be replaced by ‘*’.

replaceAll（）可以隐藏出现在字符串中的数字。 这些数字可以用“ *”代替。

public class Main {public static void main(String[] args) {String s = "Hello! this is the number : 1234 ";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceAll("[0-9]","*");System.out.println("New String: "+rep);}
}

Original String : Hello! this is the number : 1234 New String: Hello! this is the number : ****

创建自定义消息 (Creating custom messages )

replaceAll() can replace the strings in a generic string to generate a custom message. Let’s take values from a map and generate a custom message.

replaceAll（）可以替换通用字符串中的字符串以生成自定义消息。 让我们从地图中获取值并生成自定义消息。

import java.util.HashMap;
import java.util.Map;public class Main {public static void main(String[] args) {String s = "dear #Employee#, your Current Salary is #Salary#.";Map<String, String> vals = new HashMap<String, String>();vals.put("#Employee#", "John");vals.put("#Salary#", "12000");for (String key : vals.keySet()) {s = s.replaceAll(key, vals.get(key));}System.out.println(s);}
}

dear John, your Current Salary is 12000.

首先替换 (Replace First )

Unlike replceAll(), replaceFirst() only replaces the first instance of the pattern.

与replceAll（）不同，replaceFirst（）仅替换模式的第一个实例。

public class Main {public static void main(String[] args) {String s = "Welcome to JournalDev";System.out.println("Original String : "+s);System.out.println();String rep = s.replaceFirst("o","@");System.out.println("New String: "+rep);}
}

Original String: Welcome to JournalDevNew String: Welc@me to JournalDev

结论 (Conclusion)

The replaceAll() method replaces a regex with a string. This is different from the simple replace() method that only performs character substitutions. You can learn more about the repalceAll() function from its official documentation.

replaceAll（）方法将正则表达式替换为字符串。 这与仅执行字符替换的简单replace（）方法不同。 您可以从repalceAll（）函数的正式文档中了解更多信息。

翻译自: https://www.journaldev.com/41936/java-string-replaceall