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String updatedString = string.replaceFirst(null, "-") The method will throw NullPointerException if null is passed. The hashcode value is used in hashing-based collections like HashMap, HashTable etc.

The ‘null’ is Not AllowedĪ 'null' is not allowed as either method argument. Java String hashCode() method returns the hashcode for the String. String updatedString = string.replaceFirst("\\+", "-") | ? * + ()įor such metacharacters, use double backward-slash (\\) to skip that meta character. In regex, there are characters that have special meaning. Escaping Special CharactersĪlthough we can pass the regex as substring pattern to match, the original string may contain special characters that we would not want to consider in pattern matching. String s new String (Welcome) In such a case, JVM will create a new string object in normal (non-pool) heap memory and the literal Welcome will be placed in the string constant pool. String updatedString = string.replaceFirst("\\s", "-") 1) The substring() method can be used to do some prefix or suffix extraction. We can also use the regex as follows: String string = "how to do in java" The String.substring() in Java returns a new String that is a substring of the given string that begins from startIndex to an optional endIndex. String newStr = str.replaceFirst("java", "JAVA") Firstly, we’ve passed in a start index value of 0 with no end index, which. We’ll then pass integer index values to Java’s built-in substring () method. In this example, we’ll create a String object (‘Learn Java on Hackr.io ’) which we can use as a base to extract a range of substrings. The following Java program replaces the first occurrence of “java” with an uppercase “JAVA” string. Java Substring Example Using Index Values. public String substring(int startIndex): Returns a new string which start from a specified string and extends to the end of this string.