Suppose that s1 , s2 , and s3 are three strings, given as follows:

String s1 = "Welcome to Java"; String s2 = "Programming is fun"; String s3 = "Welcome to Java";

What are the results of the following expressions?

s1.charAt(0)

s1.indexOf('j')

s1.indexOf("to")

s1.lastIndexOf('a')

s1.lastIndexOf("o", 15)

s1.length()

s1.substring(5)

s1.substring(5, 11)

s1.toLowerCase()

s1.toUpperCase()

s1.concat(s2)

"\t Wel \t".trim()

Suppose that s1 and s2 are two strings. Which of the following statements or expressions are incorrect?

String s = "Welcome to Java"; String s3 = s1 + s2; String s3 = s1 - s2; s1 == s2; s1 >= s2; s1.compareTo(s2); int i = s1.length(); char c = s1(0); char c = s1.charAt(s1.length());