Question

Use java programming for the following questions to have the solutions ready within today Jan 3 2020 at or before 8:00PM GMT+8 time zone:

Question 10

1. Declare a local String variable id and initialize it with your 8-digit student ID in string form. What is the output of the following program segment?

String str = id + " "; // two spaces System.out.println(str.indexOf("5") + " + " + str.substring(0,2) + "\n"

+ str.trim().substring(5)+ "#");

2. The class List below is in java.util. What is the output of the following program segment?

List<String> aList = new Vector<>();

aList.add("one");

aList.add("two");

aList.add("three");

aList.add(2, "one");

aList.remove("one");

System.out.println(aList + "\n" + aList.size());

Answer 1

Answer

a)   Output

  It will output " index of the letter five + first two letters of the id " and on newline it prints "substring from 5 th position with a # symbol at the end"

working of each function

str.indexOf("5") - this will return the index of the first occurence of letter 5 in the id . If letter 5 is not present in id , then it will return -1

str.substring(0,2) - this will return the first two letters of the id, that is the letter at position 0 and 1

str.trim().substring(5) - trim function is used to remove the trailing and leading spaces in strings. so this will output a substring from the 5 th index of the string id which doesnt contains any leading spaces.

consider an example

if the variable   id="675439";

after executing this code
       String str = id + " "; // two spaces
       System.out.println(str.indexOf("5") + " + " + str.substring(0,2) + "\n"+ str.trim().substring(5)+ "#");

the output will be

2 + 67

9#

Here 2 is the index of letter 5 , 67 is the first two letters and 9 is the substring from 5 th index

b) Output

[two , one, three]

3

  

Reason :

aList.add("one"); -- add the string "one" to the list

after executing the below code

aList.add("one");

aList.add("two");aList.add("three");

the current list will be    [one , two, three]

aList.add(2, "one"); - this statement will add the string "one " to index 2 => 3 rd position

then the list will be  [one , two, one, three]

aList.remove("one"); - this will remove the element "one" from the string , here first occurence of one will be removed.

after that the list will be  

[two , one, three]

and its size is   3

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