 # Java Methods: Exercises, Practice, Solution

## Java Method Exercises [23 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts.]

1. Write a Java method to find the smallest number among three numbers. Go to the editor
Test Data:
Input the first number: 25
Input the Second number: 37
Input the third number: 29
Expected Output:

```The smallest value is 25.0
```

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2. Write a Java method to compute the average of three numbers. Go to the editor
Test Data:
Input the first number: 25
Input the second number: 45
Input the third number: 65
Expected Output:

```The average value is 45.0
```

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3. Write a Java method to display the middle character of a string. Go to the editor
Note: a) If the length of the string is odd there will be two middle characters.
b) If the length of the string is even there will be one middle character.
Test Data:
Input a string: 350
Expected Output:

```
The middle character in the string: 5
```

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4. Write a Java method to count all vowels in a string. Go to the editor
Test Data:
Input the string: w3resource
Expected Output:

```Number of  Vowels in the string: 4
```

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5. Write a Java method to count all words in a string. Go to the editor
Test Data:
Input the string: The quick brown fox jumps over the lazy dog.
Expected Output:

```Number of words in the string: 9
```

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6. Write a Java method to compute the sum of the digits in an integer. Go to the editor
Test Data:
Input an integer: 25
Expected Output:

```The sum is 7
```

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7. Write a Java method to display the first 50 pentagonal numbers. Go to the editor
Note: A pentagonal number is a figurate number that extends the concept of triangular and square numbers to the pentagon, but, unlike the first two, the patterns involved in the construction of pentagonal numbers are not rotationally symmetrical.
Expected Output:

```1     5     12    22    35    51    70    92    117   145
176   210   247   287   330   376   425   477   532   590
651   715   782   852   925   1001  1080  1162  1247  1335
1426  1520  1617  1717  1820  1926  2035  2147  2262  2380
2501  2625  2752  2882  3015  3151  3290  3432  3577  3725
```

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8. Write a Java method to compute the future investment value at a given interest rate for a specified number of years. Go to the editor
Sample data (Monthly compounded) and Output:
Input the investment amount: 1000
Input the rate of interest: 10
Input number of years: 5

Expected Output:

```Years    FutureValue
1            1104.71
2            1220.39
3            1348.18
4            1489.35
5            1645.31
```

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9. Write a Java method to print characters between two characters (i.e. A to P ). Go to the editor
Note: Prints 20 characters per line

Expected Output:

```( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ;
< = > ? @ A B C D E F G H I J K L M N O
P Q R S T U V W X Y Z [ \ ] ^ _ ` a b c
d e f g h i j k l m n o p q r s t u v w
x y z
```

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10. Write a Java method to check whether a year (integer) entered by the user is a leap year or not. Go to the editor

Expected Output:

```Input a year: 2017
false
```

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11. Write a Java method to check whether a string is a valid password. Go to the editor
A password must have at least ten characters.
A password consists of only letters and digits.
A password must contain at least two digits.

Expected Output:

```1. A password must have at least eight characters.
2. A password consists of only letters and digits.
3. A password must contain at least two digits
Input a password (You are agreeing to the above Terms and Conditions.): abcd1234
Password is valid: abcd1234
```

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12. Write a Java method (takes a number n as input) to displays an n-by-n matrix. Go to the editor

Expected Output:

```Input a number: 10
1 0 0 1 1 0 0 0 1 1
0 0 1 0 1 0 1 0 0 0
0 1 0 1 0 0 0 0 0 1
1 1 1 0 0 0 0 1 1 1
1 1 0 1 1 1 0 1 0 0
1 0 0 0 1 1 0 0 0 0
0 0 1 0 0 0 0 1 1 1
1 1 0 1 0 1 0 0 1 0
0 0 1 0 0 0 0 1 1 0
1 1 1 0 0 1 1 1 1 0
```

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13. Write Java methods to calculate the area of a triangle. Go to the editor

Expected Output:

```Input Side-1: 10
Input Side-2: 15
Input Side-3: 20
The area of the triangle is 72.6184377413890
```

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14. Write a Java method to create the area of a pentagon. Go to the editor

Expected Output:

```Input the number of sides: 5
Input the side: 6
The area of the pentagon is 61.93718642120281
```

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15. Write a Java method to display the current date and time. Go to the editor

Expected Output:

```Current date and time: Wednesday January 25, 2017 7:47:43
```

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16. Write a Java method to find all twin prime numbers less than 100. Go to the editor

Expected Output:

```(3, 5)
(5, 7)
(11, 13)
(17, 19)
(29, 31)
(41, 43)
(59, 61)
(71, 73)
```

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17. Write a Java method to count the number of digits in an integer that have the value 2. The integer may be assumed to be non-negative. Go to the editor

Expected Output:

```Input a number:  12541
1
```

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18. Write a Java method that accept three integers and check whether they are consecutive are not. Return true or false. Go to the editor

Expected Output:

```Input the first number:  15
Input the second number:  16
Input the third number:  17
Check whether the three said numbers are consecutive or not!true
```

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19. Write a Java method that accepts three integers and returns true if one of them is the middle point between the other two integers, otherwise false. Go to the editor

Expected Output:

```Input the first number:  2
Input the second number:  4
Input the third number:  6
Check whether the three said numbers has a midpoint!
true
```

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20. Write a Java method to develop a Java method for extracting the first digit from a positive or negative integer. Go to the editor

Expected Output:

```Input an integer(positive/negative): 1234
Extract the first digit from the said integer:
1
```

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21. Write a Java method to display the factors of 3 in a given integer. Go to the editor

Expected Output:

```Input an integer(positive/negative): 81

Factors of 3 of the said integer:
81 = 3 * 3 * 3 * 3 * 1
```

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22. Write a Java method to check whether every digit of a given integer is even. Return true if every digit is odd otherwise false. Go to the editor

Expected Output:

```Input an integer: 8642
Check whether every digit of the said integer is even or not!
true
```

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23. Write a Java method that checks whether all the characters in a given string are vowels (a, e,i,o,u) or not. Return true if each character of the string is a vowel, otherwise return false. Go to the editor

Expected Output:

```Input a string:  AIEEE
Check all the characters of the said string are vowels or not!
true
```

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## Java Code Editor

More to Come !

Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.

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## Java: Tips of the Day

everyNth:

Returns every nth element in an array.

Use IntStream.range().filter() to create a new array that contains every nth element of a given array.

```public static int[] everyNth(int[] elements, int nth) {
return IntStream.range(0, elements.length)
.filter(i -> i % nth == nth - 1)
.map(i -> elements[i])
.toArray();
}
```

Ref: https://bit.ly/3CBWdji