Strings

Question 1

‘new’ keywords stores objects in which memory type?

Answer 1

heap memory

Question 2

in which memory are literals stored?

Answer 2

pool memory

Question 3

What are the 2 ways to create a String?

Answer 3

String str = new String(“Java”)
String str = (“Java”)

Question 4

Method to check length of String?

Answer 4

int l = str.length()

Question 5

Method to find character at specified index?

Answer 5

int s = str.charAt(5)

Question 6

Method to search a character in the String from left to right and right to left?

Answer 6

str.indexOf(“k”, starting index), str.lastIndexOf(“J”,starting index)

Question 7

What are the return types of compareTo method?

Answer 7

-1: first string is smaller(smaller Ascii or comes first in alphabet)
0: both Strings are equal
+1: First string is larger(greater ascii or comes after in alphabet)

Question 8

Explain why the outputs will be different:

str1.equals(str2);
str1==str2;

Answer 8

.equals() compares the strings whereas ‘==’ compares the reference of strings.

Question 9

3 points

Why are Java Strings immutable?

Answer 9

1. Saves a lot of heap space
2. if modifiable, it won’t be secure because a hacker can modify reference value and cause security issues.
3. String is safe for multithreading because it is immutable.

Question 10

How is StringBuffer created?

Answer 10

StringBuffer sb = new StringBuffer();
StringBuffer sb = new StringBuffer(int size);
StringBuffer sb = new StringBuffer(“String”);

Question 11

Name any 5 StringBuffer methods.

Answer 11

1. append(): adds element
2. length(): returns length of sb
3. delete(beginIndex,endIndex);
4. insert(startIndex, ‘char’/”string”);
5. reverse();

Question 12

think of advantages, disadv. and when to use

3 differences between StringBuffer and StringBuilder class?

Answer 12

1. StringBuilder is not synchronized, thus not thread safe
2. Its adv. over StringBuffer is faster performance
3. When using multiThreading, StringBuffer should be used.