String Ex

Q1)
Fill in the missing codes

public class Question {
 /** returns the number of occurences of char ch in the string */
 public static int numOfChar(String string, char ch) {
 // your codes here
 }

 /** returns a new string resulting from removing all occurences of char ch */
 public static String remove(String string, char ch) {
 // your codes here
 }

 /** returns a new string resulting from moving the first n characters to the end */
 public static String move(String string, int n) {
 // your codes here
 }

 /** returns the number represented by the string */
  public static int stringToNumber(String string) {
         // we assume the string consists of only digits
         // your codes here
 } 
}

Q2)
Which of the following lines change the content of the String s.
a) s.toUpperCase();
b) s.toLowerCase();
c) s.charAt(5);
d) s.replace('a','b');
e)s.toCharArray();

Q3)
There are 2 Strings s1 and s2. Suppose System.out.println(s1) and System.out.println(s2) have the same outputs. What is the output of the following codes?

if(s1==s2) {
    System.out.println("They are equal");
}

Q4)
Suppose s1, s2 are 2 Strings. What is the difference between s1==s2 and s1.equals(s2).

Q5)
Suppose string is a String and array is an int[]. Which of the followings are correct?
a) string.length
b) string.length()
c) array.length
d) array.length()
Q5
What is the output of the following codes?
a)

public class StringTest {
    public static void main(String[] args) {
        String s = "Java is an object oriented language.";
        System.out.println(s.substring(5));
        System.out.println(s.substring(5,20));
        System.out.println(s.charAt(5));
        System.out.println(s.length());
        System.out.println(s.charAt(12));
        System.out.println(s.indexOf('a'));
        System.out.println(s.lastIndexOf('a'));
        System.out.println(s.indexOf('a', 10));
        System.out.println(s.lastIndexOf('o', 15));
        System.out.println(s.indexOf("an"));
        System.out.println(s.indexOf("an",15));
        System.out.println(s.lastIndexOf("an"));
        System.out.println(s.lastIndexOf("an", 5));
        System.out.println(s.substring(0,18).replace('a','o'));
        System.out.println(s.startsWith("Java"));
        System.out.println(s.endsWith("Java"));
    }
}

Q6)
I have a String consists of integers seperated by commas. example String s = "12,13,24,55,102,33,47,11,23,45,899,1,-5,8,23". Write a program to add all the numbers.