You need to look what System.out.println(sb); actually does. It calls in class java.io.PrintStream this method. (because a StringBuilder extends Object)

 public void println(Object x) { String s = String.valueOf(x); synchronized (this) { print(s); newLine(); } } 

And, String.valueOf(x) calls the toString() method on your StringBuilder.

public static String valueOf(Object obj) { return (obj == null) ? "null" : obj.toString(); 

}

You need to look what System.out.println(sb); actually does. It calls in class java.io.PrintStream this method. (because a StringBuilder extends Object)

 public void println(Object x) { String s = String.valueOf(x); synchronized (this) { print(s); newLine(); } } 

And, String.valueOf(x) calls the toString() method on your StringBuilder.

public static String valueOf(Object obj) { return (obj == null) ? "null" : obj.toString(); } 

You need to look what System.out.println(sb); actually does. It calls in class java.io.PrintStream this method. (because a StringBuilder extends Object)

 public void println(Object x) { String s = String.valueOf(x); synchronized (this) { print(s); newLine(); } } 

So you see String.valueOf(x) calls the toString() method on your StringBuilder.

You need to look what System.out.println(sb); actually does. It calls in class java.io.PrintStream this method. (because a StringBuilder extends Object)

 public void println(Object x) { String s = String.valueOf(x); synchronized (this) { print(s); newLine(); } } 

And, String.valueOf(x) calls the toString() method on your StringBuilder.

public static String valueOf(Object obj) { return (obj == null) ? "null" : obj.toString(); 

}