编写一个Java程序，使用For循环和While循环计算1到N的偶数和，并附有示例。任何能被2整除的数都是偶数。
Java 程序计算偶数和 示例 1
此Java程序允许用户输入最大限制值。接下来，此Java程序使用For循环和If语句计算从1到最大限制值的偶数之和。
提示：我们已经在 Java奇偶数程序 文章中的 Java 中解释了判断数字是偶数还是奇数的逻辑。
// Java Program to Calculate Sum of Even Numbers using for loop
import java.util.Scanner;
public class SumofEven1 {
private static Scanner sc;
public static void main(String[] args)
{
int number, i, evenSum = 0;
sc = new Scanner(System.in);
System.out.print(" Please Enter any Number : ");
number = sc.nextInt();
for(i = 1; i <= number; i++)
{
if(i % 2 == 0)
{
evenSum = evenSum + i;
}
}
System.out.println("\n The Sum of Even Numbers upto " + number + " = " + evenSum);
}
}
首先，我们使用For循环从1迭代到最大值（此处，number = 5）。接下来，使用 If条件 来检查数字除以2的余数是否正好等于0。
用户为此Java程序输入的查找偶数和的值：number = 5
For 循环第一次迭代：for(i = 1; i <= 5; i++)
if(i % 2 == 0) => if(1 % 2 == 0) – 条件为 False
第二次迭代：for(i = 2; 2 <= 5; 2++)
if(2 % 2 == 0) – 条件为 True。
evenSum = evenSum + i
evenSum = 0 + 2 = 2
第三次迭代：for(i = 3; 3 <= 5; 3++)
if(3 % 2 == 0) – False
第四次迭代：for(i = 4; 4 <= 5; 4++)
if(4 % 2 == 0) – True。
evenSum = evenSum + i
evenSum = 2 + 4 = 6
第五次迭代：for(i = 5; 5 <= 5; 5++)
if(5 % 2 == 0) – False
第六次迭代：for(i = 6; 6 <= 5; 6++)
条件 (6 <= 5) 为 False。因此，Java 编译器退出 For 循环
Java 程序计算偶数和 示例 2
在此Java程序中，我们使用了不带 If语句 的for循环。如果您观察下面的Java代码，我们从2开始i，并以2递增（而不是1）。这意味着，第一次迭代i = 2，第二次迭代i = 4（而不是3），依此类推。
// Java Program to Calculate Sum of Even Numbers
import java.util.Scanner;
public class SumofEven2 {
private static Scanner sc;
public static void main(String[] args)
{
int number, i, evenSum = 0;
sc = new Scanner(System.in);
System.out.print(" Please Enter any Number : ");
number = sc.nextInt();
for(i = 2; i <= number; i = i + 2)
{
evenSum = evenSum + i;
}
System.out.println("\n The Sum of Even Numbers upto " + number + " = " + evenSum);
}
}
Java 使用for循环计算偶数和 输出
Please Enter any Number : 25
The Sum of Even Numbers upto 25 = 156Java 程序计算偶数和 示例 3
这个查找偶数和的Java程序与第二个示例相同，但我们使用了 While 循环。
// Java Program to find Sum of Even Numbers using While Loop
import java.util.Scanner;
public class SumofEven5 {
private static Scanner sc;
public static void main(String[] args)
{
int number, i = 2, evenSum = 0;
sc = new Scanner(System.in);
System.out.print(" Please Enter any Number : ");
number = sc.nextInt();
while(i <= number)
{
evenSum = evenSum + i;
i = i + 2;
}
System.out.println("\n The Sum of Even Numbers upto " + number + " = " + evenSum);
}
}
Please Enter any Number : 35
The Sum of Even Numbers upto 35 = 306Java 程序使用方法计算偶数和
此程序与第一个示例相同。但我们将逻辑分开并将其放在一个单独的方法中。
// Java Program to find Sum of Even Numbers
import java.util.Scanner;
public class SumofEven3 {
private static Scanner sc;
public static void main(String[] args)
{
int number, evenSum = 0;
sc = new Scanner(System.in);
System.out.print(" Please Enter any Number : ");
number = sc.nextInt();
evenSum = sumOfEven(number);
System.out.println("\n The Sum of Even Numbers upto " + number + " = " + evenSum);
}
public static int sumOfEven(int num)
{
int i, sum = 0;
for(i = 1; i <= num; i++)
{
if(i % 2 == 0)
{
sum = sum + i;
}
}
return sum;
}
}
Please Enter any Number : 45
The Sum of Even Numbers upto 45 = 506Java 程序查找给定范围内的偶数和
此Java程序允许用户输入最小值和最大值。接下来，Java程序计算最小值和最大值之间的偶数之和。
// Java Program to Calculate Sum of Even Numbers between Maximum and Minimum
import java.util.Scanner;
public class SumofEven4 {
private static Scanner sc;
public static void main(String[] args)
{
int minimum, maximum, evenSum = 0;
sc = new Scanner(System.in);
System.out.print(" Please Enter the Minimum value : ");
minimum = sc.nextInt();
System.out.print(" Please Enter the Maximum value : ");
maximum = sc.nextInt();
evenSum = sumOfEven(minimum, maximum);
System.out.println("\n The Sum of Even Numbers from " + minimum + " to " + maximum + " = " + evenSum);
}
public static int sumOfEven(int minimum, int maximum)
{
int i, sum = 0;
if(minimum % 2 != 0)
{
minimum++;
}
for(i = minimum; i <= maximum; i++)
{
if(i % 2 == 0)
{
sum = sum + i;
}
}
return sum;
}
}
Please Enter the Minimum value : 10
Please Enter the Maximum value : 75
The Sum of Even Numbers from 10 to 75 = 1386请参考