Here in this context We can directly pass String class object to StringBuffer and StringBuilder class constructors. As String class is immutable in java, so for editing a string, we can perform same by converting it to StringBuffer or StringBuilder class objects.

Example.java

public class Example {
	public static void main(String[] args) {
		String str = "SILAN";
		//Conversion from String object to StringBuffer
		StringBuffer sb1 = new StringBuffer(str);
		System.out.println(sb1);
		sb1.reverse();
		System.out.println(sb1);
		//Conversion from String object to StringBuilder
		StringBuilder sb2 = new StringBuilder(str);
		sb2.append("Software");
		System.out.println(sb2);
	}
}

Output:

SILAN

NALIS

SILANSoftware