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Why Isn't My Java String Replace Method Updating the String?

Linda HamiltonOriginal: 2024-11-14 11:48:02586browse

Java String Replace Method Behaving Unexpectedly

In Java, the String replace method is a commonly used function for replacing occurrences of a substring with a new string. However, sometimes users encounter situations where the replace method appears to be malfunctioning.

Consider the following code snippet:

String delimiter = "\*\*";
String html = "<html><head></head><body>**USERNAME** AND **PASSWORD**</body></html>";
Map<String, String> mp = new HashMap<>();
mp.put("USERNAME", "User A");
mp.put("PASSWORD", "B");
for (Entry<String, String> entry : mp.entrySet()) {
  html.replace(delimiter + entry.getKey()+ delimiter, entry.getValue());
}

In this code, the goal is to replace the placeholders for USERNAME and PASSWORD in the HTML string with the corresponding values from the map provided. However, upon execution, the original HTML string html remains untouched, leading to困惑ion.

Understanding the Issue

To understand the issue, we need to remember that Strings in Java are immutable, meaning they cannot be modified in place. The replace method on strings returns a new String object containing the modified values. In our code, we are not capturing the result of the replace method and assigning it back to the original html variable. As a result, the changes are not being applied to the original string.

Solution

To resolve this issue, we need to capture the result of the replace method and assign it back to the html variable:

html = html.replace(delimiter + entry.getKey()+ delimiter, entry.getValue());

With this modification, the code will now correctly update the html string with the desired replacement values.

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Why Isn't My Java String Replace Method Updating the String?

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