1
00:00:00,270 --> 00:00:03,000
A bullet is only useful if you write it as a comparison.

2
00:00:04,430 --> 00:00:06,290
So far, we covered every data type.

3
00:00:06,500 --> 00:00:13,010
There are more, but these are the most common int long double drinka and bullion.

4
00:00:13,940 --> 00:00:16,460
Now all of these types look like they serve a purpose.

5
00:00:16,460 --> 00:00:19,610
But what's useful about a variable that can only store true or false?

6
00:00:20,650 --> 00:00:26,320
Well, the way that you learn how to store them is pretty useless, a boolean value is only useful if

7
00:00:26,320 --> 00:00:27,850
in the form of a comparison.

8
00:00:30,770 --> 00:00:35,030
So in this lesson, you're going to write comparisons that return either true or false.

9
00:00:36,850 --> 00:00:41,350
First thing I'm going to do is create a new class inside the section refold or create a new file named

10
00:00:41,350 --> 00:00:47,710
Boolean comparison's Java and in the Boolean comparisons class, make sure it has the main method.

11
00:00:53,950 --> 00:01:01,270
So what is a comparison, a comparison compares to values, then it returns true or false?

12
00:01:02,880 --> 00:01:08,610
So instead of writing static, true or false values, a comparison will return true if what you write

13
00:01:08,610 --> 00:01:12,900
is true and conversely, it's going to return false if what you write is false.

14
00:01:13,530 --> 00:01:16,890
So, for example, this first comparison checks a five is bigger than one.

15
00:01:17,310 --> 00:01:18,150
That is true.

16
00:01:18,660 --> 00:01:21,370
The second comparison checks of five is less than one.

17
00:01:21,480 --> 00:01:22,560
This is false.

18
00:01:25,430 --> 00:01:31,520
And there are eight types of comparisons we can make greater than less than greater than or equal to

19
00:01:31,790 --> 00:01:39,500
less than or equal to, equal to not equal to equal to four string values and not equal to four string.

20
00:01:40,970 --> 00:01:45,260
We're going to go through all of them, but first we'll start by discussing the greater than comparison.

21
00:01:46,330 --> 00:01:52,300
This comparison involves a value on the left be greater than comparison, any value on the right.

22
00:01:53,410 --> 00:01:57,130
The greater then operator compares the value on the left to the value on the right.

23
00:01:57,550 --> 00:02:01,150
If the value on the left is greater, the comparison returns true.

24
00:02:01,660 --> 00:02:03,900
If not, the comparison is false.

25
00:02:08,259 --> 00:02:14,230
You can compare any type of value like int longer double, so we'll start by making two and variables

26
00:02:14,230 --> 00:02:15,670
int chemistry grade.

27
00:02:19,580 --> 00:02:24,890
Is equal to 95 and into biology grade is equal to 75.

28
00:02:30,210 --> 00:02:34,600
Now, your friend Harry wants to check if he did better in biology, and we're going to help him out.

29
00:02:35,220 --> 00:02:37,170
We're going to check if biology grade.

30
00:02:41,960 --> 00:02:43,790
Is greater than chemistry grade.

31
00:02:47,980 --> 00:02:49,720
And as I run my code.

32
00:03:02,070 --> 00:03:03,600
And this clearly is false.

33
00:03:06,110 --> 00:03:11,090
Java checks, if Buyology great is greater than chemistry and this comparison is not true, it's false.

34
00:03:15,330 --> 00:03:22,920
You can also compare decimals, so we're going to make two double variables, double sales is equal

35
00:03:22,920 --> 00:03:24,570
to thirty seven point five five.

36
00:03:25,620 --> 00:03:29,730
And double castes is equal to 5.5 five.

37
00:03:32,160 --> 00:03:36,520
And we're going to check if the school made money, that is our sales greater than costs.

38
00:03:37,240 --> 00:03:43,150
So we're going to print the comparison of checking sales being greater than costs.

39
00:03:44,810 --> 00:03:45,980
We're going to run the code.

40
00:03:57,060 --> 00:04:01,230
And as we do, this is a true comparison, sales are greater than costs.

41
00:04:03,220 --> 00:04:07,790
You greater than comparison returns, true, because the value on the left is greater than the value

42
00:04:07,790 --> 00:04:08,420
on the right.

43
00:04:12,110 --> 00:04:13,820
Onto the less than comparison.

44
00:04:15,300 --> 00:04:21,930
This comparison involves a value on the left, the less than operator and the value on the right now,

45
00:04:21,930 --> 00:04:24,910
less then compares the value on the left to the value on the right.

46
00:04:25,200 --> 00:04:28,100
If the value on the left is less, the comparison is true.

47
00:04:28,560 --> 00:04:30,810
Otherwise, the comparison returns false.

48
00:04:32,470 --> 00:04:35,740
So we're going to reverse the grittier then comparisons with less than.

49
00:04:42,510 --> 00:04:43,500
Rerun our code.

50
00:04:49,220 --> 00:04:53,510
And accordingly, the first comparison is true and the second one is false.

51
00:04:55,190 --> 00:04:59,570
The first comparison is true because biology grade is indeed less than the chemistry grade.

52
00:05:04,540 --> 00:05:08,740
The second comparison checks if sales are less than costs and this is false.

53
00:05:13,470 --> 00:05:16,980
All right, now we're going to remove the sales and cost variable because we're not going to need them

54
00:05:16,980 --> 00:05:17,340
anymore.

55
00:05:20,210 --> 00:05:22,670
Onto the greater than or equal to comparison.

56
00:05:23,800 --> 00:05:29,560
Once again, this involves a value on the left, the greater than or equal to the operator, any value

57
00:05:29,560 --> 00:05:34,960
on the rights would be greater than or equal to comparison checks if the value on the left is greater

58
00:05:34,960 --> 00:05:36,820
than or equal to the value on the rights.

59
00:05:37,300 --> 00:05:41,290
If so, the comparison is true, and if not, the comparison is false.

60
00:05:42,010 --> 00:05:47,230
So we're going to add a new variable English grade and we're going to set it equal to seventy five.

61
00:05:50,870 --> 00:05:53,060
And we're going to check if chemistry grade.

62
00:05:55,730 --> 00:05:58,280
Is greater than or equal to the English great.

63
00:06:02,340 --> 00:06:03,240
Runnier code.

64
00:06:07,270 --> 00:06:13,210
And this comparison returns true, that's because chemistry grade, the value on the left is greater

65
00:06:13,210 --> 00:06:16,710
than Englis grade, which results in a true comparison.

66
00:06:18,350 --> 00:06:20,510
Now we're going to compare it with the biology grade.

67
00:06:26,320 --> 00:06:29,800
So check if biology grade is greater than or equal to English grade.

68
00:06:34,700 --> 00:06:35,630
Run your code.

69
00:06:38,910 --> 00:06:44,880
And once again, this is the comparison is true because English grant is equal to biology grade.

70
00:06:47,870 --> 00:06:53,920
Onto the less than or equal to comparison this one checks, if I'm sure you get the pattern by now,

71
00:06:54,410 --> 00:06:58,930
there is a value on the left the less than or equal to comparison, any value on the right.

72
00:06:59,360 --> 00:07:01,210
And you can probably assume what this does.

73
00:07:01,940 --> 00:07:05,660
So we're going to switch every operator with a less than or equal to comparison.

74
00:07:10,320 --> 00:07:11,430
We run our code.

75
00:07:16,480 --> 00:07:20,050
And that's interesting, the comparison returns false then true.

76
00:07:21,420 --> 00:07:26,550
The first comparison checks, if chemistry rate is less than or equal to wingless grade, this is false

77
00:07:26,550 --> 00:07:28,200
because chemistry grade is greater.

78
00:07:30,000 --> 00:07:34,770
And the second comparison is true, because biology grade is indeed equal to English grade.

79
00:07:39,460 --> 00:07:44,590
And now there's the equal comparison which returns true, if the values are equal, it returns false.

80
00:07:44,590 --> 00:07:50,440
Otherwise, as always, there's a value on the left, the double equals sign any value on the rights.

81
00:07:53,370 --> 00:07:56,400
So we're going to replace every operator with the equals comparison.

82
00:07:59,310 --> 00:08:00,270
Rerun your code.

83
00:08:05,610 --> 00:08:10,980
And we get the same results, but for different reasons, the first comparison checks if chemistry grade

84
00:08:10,980 --> 00:08:16,830
is equal to English grade, which is false, and biology grade is indeed equal to the English grade.

85
00:08:16,830 --> 00:08:18,120
So that returns true.

86
00:08:21,170 --> 00:08:27,890
Onto the not equal comparison, the exclamation mark in Java means not this makes our operator the not

87
00:08:27,890 --> 00:08:31,310
equal comparison and do not equal comparison returns.

88
00:08:31,310 --> 00:08:33,740
True, if the values are not equal, it returns.

89
00:08:33,740 --> 00:08:34,640
False if they are.

90
00:08:35,630 --> 00:08:40,650
As you probably guessed, it involves a value on the left, the not equal comparison, any value on

91
00:08:40,650 --> 00:08:41,070
the right.

92
00:08:44,620 --> 00:08:48,670
So back in her coat, we're going to replace the operators with the not equal to comparison.

93
00:08:51,280 --> 00:08:52,540
We're going to rerun our code.

94
00:08:55,980 --> 00:08:58,650
And as you could predict, the results switch.

95
00:09:01,240 --> 00:09:05,050
Now, the first comparison is true because chemistry does not equal to English grade.

96
00:09:07,830 --> 00:09:12,450
And the second comparison checks at Balaji grade is not equal to English grade, and that's false.

97
00:09:12,630 --> 00:09:13,470
They are equal.

98
00:09:15,410 --> 00:09:21,170
The equals method checks, if string values are equal, the equals method is the same as the equal sign,

99
00:09:21,170 --> 00:09:22,500
but it's four string values.

100
00:09:23,360 --> 00:09:27,950
With that being said, never used the double equals sign or the not equal sine comparisons.

101
00:09:27,950 --> 00:09:31,430
To compare string values, you will get inconsistent results.

102
00:09:32,040 --> 00:09:37,730
The equals comparison four strings involves a string value on the left and equals method that checks

103
00:09:37,820 --> 00:09:40,070
the string on the left is equal to the string on the right.

104
00:09:40,070 --> 00:09:41,720
Any string value on the rights.

105
00:09:43,040 --> 00:09:47,930
So we're going to make two string variables and assign them the same string value, string sentence.

106
00:09:48,290 --> 00:09:50,810
We're going to set an equal to I love this course.

107
00:09:56,460 --> 00:09:59,270
And we're going to make another variable that equals the same thing.

108
00:10:09,230 --> 00:10:11,570
Now I'm going to compare them using the equals method.

109
00:10:12,410 --> 00:10:17,660
We're going to print the result of checking if sentence equals sentence to.

110
00:10:26,530 --> 00:10:27,520
We were on your code.

111
00:10:36,400 --> 00:10:40,150
And this is indeed true, both strong values are equal.

112
00:10:42,470 --> 00:10:46,700
And the last method we're going to look at is did not equals method, not equals method.

113
00:10:46,700 --> 00:10:48,590
Checks of string values are not equal.

114
00:10:48,860 --> 00:10:51,380
Remember that the exclamation mark in Java means not.

115
00:10:51,590 --> 00:10:53,990
So this makes our method is not equals method.

116
00:10:54,850 --> 00:10:57,880
So we're going to add an exclamation mark and we'll run honor code.

117
00:11:03,580 --> 00:11:08,860
As we expect, the results should switch because the comparison checks, if the strong values are not

118
00:11:08,860 --> 00:11:11,950
equal but the strong values are equal, so it's false.

119
00:11:13,630 --> 00:11:17,780
Finally, I want to make sure that you don't confuse the equal signs with the single equal sign.

120
00:11:18,010 --> 00:11:19,720
They are very, very different.

121
00:11:20,300 --> 00:11:23,470
A single equal sign sets a variable equal to another value.

122
00:11:24,250 --> 00:11:26,100
The equal sign is a comparison.

123
00:11:26,140 --> 00:11:28,630
It compares to values and returns a boolean.

124
00:11:28,630 --> 00:11:29,800
True or false?

125
00:11:32,740 --> 00:11:37,720
In this lesson, you make comparisons that return true or false, instead of writing static, true or

126
00:11:37,720 --> 00:11:40,150
false values, a comparison will return true.

127
00:11:40,150 --> 00:11:45,910
If what you write is true, just like this comparison, any comparison will return false if what you

128
00:11:45,910 --> 00:11:46,870
write is false.

129
00:11:47,680 --> 00:11:52,390
You saw that there are eight comparison operators and in this lesson you made comparisons from all of

130
00:11:52,390 --> 00:11:52,610
them.

131
00:11:53,410 --> 00:11:55,980
Now you might be asking why are comparisons useful?

132
00:11:55,990 --> 00:11:57,050
How can we use them?

133
00:11:57,490 --> 00:12:01,240
Well, stick around as we expand into F.L. statements.