Notes

! Overiiden mehtods doesn't throw any checked exceptions

Collections!

A Collection is a group of objects. Collections framework provides a set of standard utility classes to manage collections. Collections Framework consists of three parts:

• Core Interfaces
• Concrete Implementation
• Algorithms such as searching and sorting

package com;
								
								public class TestEmployee {
								
									public static void main(String[] args) {
								
										Employee emp = new Employee("Sai");
										Employee emp1 = new Employee("Sai");
										System.out.println(emp);
										System.out.println(emp1);
								
										System.out.println(emp.equals(emp1));
								
										String s = new String("Hi");
										String s1 = new String("Hi");
								
										System.out.println(s1.equals(s));
									}
								
								}
								

Two different objects can have same hashcodes

So for checking equality, we use equals. Such as in sets, which doesn't allow duplicate values.

	Not ordered and not sorted in hashcode	Hashcode

Creating heterogenious collections is not recommended

If hashcode of the two objects are equals, then only equals method is called

Problems

The string may be any length, including 0.
	withouEnd2("Hello") → "ell"
	withouEnd2("abc") → "b"
	withouEnd2("ab") → ""
	

Given a string of even length, 
	return a string made of the middle two chars, 
	so the string "string" yields "ri". 
	The string length will be at least 2.
	
	middleTwo("string") → "ri"
	middleTwo("code") → "od"
	middleTwo("Practice") → "ct"
	

Given a string, return true if it ends in "ly".
	
	
	endsLy("oddly") → true
	endsLy("y") → false
	endsLy("oddy") → false
	

Given a string and an int n, 
	return a string made of the first and last n chars from the string. 
	The string length will be at least n.
	
	
	nTwice("Hello", 2) → "Helo"
	nTwice("Chocolate", 3) → "Choate"
	nTwice("Chocolate", 1) → "Ce"
	

Given a string of odd length, return the string length 3 from its middle, 
	so "Candy" yields "and". The string length will be at least 3.
	
	
	middleThree("Candy") → "and"
	middleThree("and") → "and"
	middleThree("solving") → "lvi"
	

Given two strings, word and a separator sep,
	 return a big string made of count occurrences of the word, 
	separated by the separator string.
	
	
	repeatSeparator("Word", "X", 3) → "WordXWordXWord"
	repeatSeparator("This", "And", 2) → "ThisAndThis"
	repeatSeparator("This", "And", 1) → "This"
	

A sandwich is two pieces of bread with something in between. 
	Return the string that is between the first and last appearance of "bread" 
	in the given string, or return the empty string "" 
	if there are not two pieces of bread.
	
	
	getSandwich("breadjambread") → "jam"
	getSandwich("xxbreadjambreadyy") → "jam"
	getSandwich("xxbreadyy") → ""
	

Returns true if for every '*' (star) in the string, if there are chars both 
	immediately before and after the star, they are the same.
	
	
	sameStarChar("xy*yzz") → true
	sameStarChar("xy*zzz") → false
	sameStarChar("*xa*az") → true
	
	

We'll say that a "triple" in a string is a char appearing three times in a row. 
	Return the number of triples in the given string. The triples may overlap.
	
	
	countTriple("abcXXXabc") → 1
	countTriple("xxxabyyyycd") → 3
	countTriple("a") → 0
	

Given a string, return the sum of the digits 0-9 that appear in the string, 
	ignoring all other characters. Return 0 if there are no digits in the string. 
	(Note: Character.isDigit(char) tests if a char is one of the chars '0', '1', .. '9'. Integer.parseInt(string) converts a string to an int.)
	
	
	sumDigits("aa1bc2d3") → 6
	sumDigits("aa11b33") → 8
	sumDigits("Chocolate") → 0