how to replace different words in java from string code example

Example 1: java replace character in string

String s = "new String";
String replaced = s.replace("new","Test");
							  ^		 ^
                             old    new char

Example 2: how to count an replace string in java

public static void main(String[] args) throws Exception {
        String word = "abcdefg";
        System.out.println(word.length());
        System.out.println(word.replace("a", "").length());
        int a_counter = word.length() - word.replace("a", "").length();
        System.out.println(a_counter);
}