Java Program to Print the First 100 Even and Odd Numbers
An even number divides by 2 with no remainder (2, 4, 6, ...), and an odd number leaves a remainder of 1 (1, 3, 5, ...). The first 100 even numbers are 2 to 200, and the first 100 odd numbers are 1 to 199.
1. Print the First 100 Even Numbers
The n-th even number is 2 × n, so a loop from 1 to 100 that prints 2 * i gives exactly the first 100 even numbers. printf("%4d") keeps the columns aligned, with 10 numbers per line.
public class First100Even {
public static void main(String[] args) {
System.out.println("First 100 even numbers:");
for (int i = 1; i <= 100; i++) {
System.out.printf("%4d", 2 * i);
if (i % 10 == 0) {
System.out.println();
}
}
}
}Output
First 100 even numbers: 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 122 124 126 128 130 132 134 136 138 140 142 144 146 148 150 152 154 156 158 160 162 164 166 168 170 172 174 176 178 180 182 184 186 188 190 192 194 196 198 200
2. Print the First 100 Odd Numbers
Here the loop starts at 1 and steps by 2, so it visits only odd numbers. A counter stops it after 100 numbers.
public class First100Odd {
public static void main(String[] args) {
System.out.println("First 100 odd numbers:");
int count = 0;
for (int n = 1; count < 100; n += 2) {
System.out.printf("%4d", n);
count++;
if (count % 10 == 0) {
System.out.println();
}
}
}
}Output
First 100 odd numbers: 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 125 127 129 131 133 135 137 139 141 143 145 147 149 151 153 155 157 159 161 163 165 167 169 171 173 175 177 179 181 183 185 187 189 191 193 195 197 199
3. Even and Odd Numbers in a Range Using %
To split any range into even and odd numbers, test each number with n % 2 == 0. This program collects both lists in StringBuilder objects and prints them with their counts.
import java.util.Scanner;
public class EvenOddInRange {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Start: ");
int start = scanner.nextInt();
System.out.print("End: ");
int end = scanner.nextInt();
scanner.close();
StringBuilder even = new StringBuilder();
StringBuilder odd = new StringBuilder();
int evenCount = 0, oddCount = 0;
for (int n = start; n <= end; n++) {
if (n % 2 == 0) {
even.append(n).append(' ');
evenCount++;
} else {
odd.append(n).append(' ');
oddCount++;
}
}
System.out.println("Even (" + evenCount + "): " + even);
System.out.println("Odd (" + oddCount + "): " + odd);
}
}Output (with sample input)
Start: 11 End: 30 Even (10): 12 14 16 18 20 22 24 26 28 30 Odd (10): 11 13 15 17 19 21 23 25 27 29
4. Summary
- The first 100 even numbers are
2 * iforifrom 1 to 100 (2 to 200). - The first 100 odd numbers start at 1 and go up in steps of 2 (1 to 199).
n % 2 == 0tells whether any number is even.- Use
printf()with a width such as%4dto print the numbers in neat columns.
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