Strings Are Different

Some strings are different, even though they look like the same. See the following codes:

public class Strings {
    public static void main(String[] args) {
        String s1 = "42";
        char[] a = new char[100];
        a[99] = '2';
        a[98] = '4';
        String s2 = new String(a);
        String s3 = s2.substring(98);
        System.out.println("s1 = " + s1);
        System.out.println("s2 = " + s2);
        System.out.println("s3 = " + s3);
        System.out.println("s1.length() = " + s1.length());
        System.out.println("s2.length() = " + s2.length());
        System.out.println("s3.length() = " + s3.length());
        System.out.println("s1 == s2 = " + s1.equals(s2));
        System.out.println("s1 == s3 = " + s1.equals(s3));
    }
}

And the output:

s1 = 42
s2 = 42
s3 = 42
s1.length() = 2
s2.length() = 100
s3.length() = 2
s1 == s2 = false
s1 == s3 = true

The reason is that in s2 there are unprintable ascii characters like NUL.