for循环语句全示例

阳光穿透心脏的1/2处 2022-02-28 15:36 243阅读 0赞

代码  
if-else语句  
import java.util.Scanner;

public class demo01 \{  
public static void main(String\[\] args) \{  
int x = 0;  
Scanner sc = new Scanner([System.in][]);  
x = sc.nextInt();  
if (x <= 1) \{

System.out.println(x);
        } else if (x > 1 & x < 10) {
            System.out.println(3 * x - 2);
        } else {
            System.out.println(4 * x);
        }
    }

\}  
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for循环语句  
1+3+7+…+(2n-1)  
/\*

*  1+3+7+…+(2^n-1)  
    */  
    public class demo02 \{  
    public static void main(String\[\] args) \{  
    int sum = 0;  
    int a = 1;  
    for (int i = 1; i <= 20; i++) \{  
    // int a=0;  
    // a=a*2+1;  
    // sum=sum+a;  
    a = a \* 2;  
    sum = sum + a - 1;  
    \}  
    System.out.println(sum);  
    \}

\}  
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输出1+2+4+…+10000（忽略末位数为3的数）  
/\*

*  1+2+4+…+10000忽略末位数为3的数  
    */  
    public class demo03 \{  
    public static void main(String\[\] args) \{  
    int sum = 0;  
    for (int i = 1; i <= 10000; i++) \{  
    if (i % 10 == 3) \{  
    continue;  
    \}  
    sum = sum + i;  
    \}  
    System.out.println(sum);  
    \}  
    \}  
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    打印金字塔  
    import java.util.Scanner;  
    /*
 *  打印金字塔  
    */  
    public class demo04 \{  
    public static void main(String\[\] args) \{  
    int count=0;  
    Scanner sc = new Scanner([System.in][]);  
    System.out.print(“请输入你要打印的排数：”);  
    count = sc.nextInt();  
    for(int i=1;i<=count ;i++)\{  
    for(int j=0;j<=count-i;j++)\{  
    System.out.print(" ");  
    \}  
    for(int j=1;j<=2*i-1;j++)\{  
    System.out.print("\*");  
    \}  
    System.out.print("\\n");  
    \}  
    \}

\}  
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打印九九乘法表  
/\*

*  打印九九乘法表  
    */  
    public class demo05 \{  
    public static void main(String\[\] args) \{  
    System.out.println(“九九乘法表”);  
    for(int i=1;i<=9 ;i++)\{  
    for(int j=1;j<=i;j++)\{  
    System.out.print(j+“x”+i+"="+i*j+"\\t");  
    \}  
    System.out.println(" ");  
    \}  
    \}  
    \}  
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    输出1—1000以内的素数  
    /\*
 *  输出1——1000以内的素数  
    \*/  
    public class demo06 \{  
    public static void main(String\[\] args) \{  
    for (int i = 1; i <= 1000; i++) \{  
    int count = 0;// 被整除的次数  
    for (int j = 1; j <= Math.sqrt(i); j++) \{  
    if (i % j == 0) \{  
    count++;  
    \}  
    \}  
    if (count <= 2) \{  
    System.out.println(i);  
    \}  
    \}  
    \}  
    \}  
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    另外一种比较好的方法：

public class demo07 \{  
public static void main(String\[\] args) \{  
for (int i = 1; i <= 1000; i++) \{  
boolean isSushu=true;

for (int j = 2; j <= Math.sqrt(i); j++) {
                if (i % j == 0) {
                    isSushu =false;
                    break;
                }
            }
            if (isSushu) {
                System.out.println(i);
            }
        }
    }

\}  
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求1—1000以内的完全数  
/\*

*  求1——1000以内的完全数  
    */  
    public class demo08 \{  
    public static void main(String\[\] args) \{  
    for (int i = 1; i <= 1000; i++) \{  
    int sum = 0;  
    for (int j = 1; j <i; j++) \{  
    if (i % j == 0) \{  
    sum = sum + j;// 此时j是i的因子  
    \}  
    \}  
    if (sum == i) \{  
    System.out.println(i);  
    \}  
    \}  
    \}  
    \}  
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    生兔子问题  
    /*
 *  现有一对成熟的兔子，一对成熟的兔子每个月生一对兔子，小兔子三个月长成为成熟的兔子
 *  求20个月后的兔子总对数  
    \*/  
    public class demo09 \{  
    public static void main(String\[\] args) \{  
    int a = 1;  
    int b = 2;  
    int c = 3;  
    int temp;  
    for (int i =4; i <= 20; i++) \{  
    temp = a + c;  
    a = b;  
    b = c;  
    c = temp;  
    System.out.println(“第”+i+“个月生的兔子对数为”+temp+“对”);  
    \}  
    \}  
    \}  
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    拓展  
    打印实心菱形  
    import java.util.Scanner;

public class demo11 \{  
public static void main(String\[\] args) \{  
int count = 0;  
Scanner sc = new Scanner([System.in][]);  
System.out.print(“请输入你要打印的总行数：”);  
count = sc.nextInt();

System.out.println("实心菱形：");//count为总行数，i为第几行数
        for (int i = 1; i <= count; i++) {
            if (i <= count / 2 + 1) {
                for (int j = 1; j <= count / 2 + 1 - i; j++) {
                    System.out.print(" ");
                }
                for (int j = 1; j <= i; j++) {
                    System.out.print("* ");
                }
                System.out.println();
            } else {
                for (int j = 1; j <= (i - (count / 2 + 1)); j++){
                    System.out.print(" ");
                }
                for(int j = 1; j <= (2*(count / 2 + 1) - i);j++){
                    System.out.print("* ");
                }
                System.out.println();
            }
        }
    }

\}  
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打印空心菱形  
import java.util.Scanner;

public class demo10 \{  
public static void main(String\[\] args) \{  
int count = 0;  
Scanner sc = new Scanner([System.in][]);  
System.out.print(“请输入你要打印的总行数：”);  
count = sc.nextInt();

System.out.println("空心菱形：");//i为第几行数，count为总行数
        for (int i = 1; i <= (count / 2 + 1); i++) {
            for (int j = 1; j <= ((count / 2 + 1) - i); j++) {
                System.out.print(" ");
            }
            System.out.print("*");
            for (int j = 1; j <= ((i - 2) * 2 + 1); j++) {
                System.out.print(" ");
            }
            if (i != 1) {
                System.out.print("*");
            }
            System.out.println();
        }
        for (int i = (count / 2); i >= 1; i--) {
            for (int j = 1; j <= ((count / 2 + 1) - i); j++) {
                System.out.print(" ");
            }
            System.out.print("*");
            for (int j = 1; j <= ((i - 2) * 2 + 1); j++) {
                System.out.print(" ");
            }
            if (i != 1) {
                System.out.print("*");
            }
            System.out.println();
        }
    }

## \} ##

作者：木大白易  
来源：CSDN  
原文：[https://blog.csdn.net/aiynmimi/article/details/46917077][https_blog.csdn.net_aiynmimi_article_details_46917077]

[System.in]: http://System.in
[https_blog.csdn.net_aiynmimi_article_details_46917077]: https://blog.csdn.net/aiynmimi/article/details/46917077