How does sb2 in the below code holds abc but not abcd?

Question

    StringBuffer sb1 = new StringBuffer("abc");
    StringBuffer sb2 = new StringBuffer(sb1);

    sb1.append("d");

    System.out.println(sb2);

Since StringBuffer is mutable and sb2 points to sb1, i would expect sb2 to have "abcd" as the value. Though the question is layman, could you please help me explain this.

Answer 1

StringBuffer creates a new object in Heap on calling new StringBuffer(sb1). It does not point to sb1.
If you wish to make sb2 point to sb1, then declare StringBuffer sb2 = sb1

public StringBuffer(String str)

Constructs a string buffer initialized to the contents of the specified string. The initial capacity of the string buffer is 16 plus the length of the string argument.