String Replace in Java

In Java, you can replace part of a string using the replace() method:

s.replace(old, new)          // replaces all occurrences
s.replaceFirst(regex, new)   // replaces first match

Here are some examples:

String sentence = "I love cats";
String result = sentence.replace("cats", "dogs");
System.out.println(result);  // "I love dogs"

String text = "aaa";
System.out.println(text.replace("a", "b"));  // "bbb"

replace() returns a new String — the original is not modified.