java 使用for循环打印杨辉三角形

首先需要说明的问题: 什么是杨辉三角形?

如图所示:杨辉三角形由数字排列,基本的特点是两侧的数值均为1,其它位置的数值是基正上方的数值与其左上方的数值之和.

代码实现:

package test;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.PrintStream;

import java.util.Scanner;

public class Demo{public static void main(String[] args) throws Exception{

//        scanner();

//        redirectOutputStream();

//        encode();

        triangle();

    }

    @SuppressWarnings("resource")

    public static void scanner()

    {

        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入你的名字:");

        String line = scanner.nextLine();

        System.out.println(line);

    }

    public static void redirectOutputStream(){

　　　　　//重定向系统输出流

        //D:\Users\Hoonick_Cheng\Desktop\stack.txt

        try

        {

            PrintStream out = System.out;

            String filePath = "D:"+ File.separator + "Users"+File.separator

                    +"Hoonick_Cheng"+File.separator+"Desktop"+File.separator+"log.txt";

            PrintStream ps = new PrintStream(filePath);

            System.setOut(ps);

            int age = 18;

            System.out.println("定义对象年龄为: " + age);

            String sex = "男";

            System.out.println("定义对象性别为: " + sex);

            String info = "这是个" + sex + "孩子,已经" + age + "岁了!";

            System.out.println("整合两个变量为: " + info);

            System.setOut(out);

            System.out.println("程序运行完毕,请查看日志文档!");

        }

        catch (FileNotFoundException e)

        {

            e.printStackTrace();

        }

    }

    public static void encode(){

        //数A与数B异或两次得到的还是A,可以用于简单的加密解密

        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入一个英文字符串或解密字符串:");

        String password = scanner.nextLine();

        char[] charArray = password.toCharArray();

        for (int i = 0; i < charArray.length; i++)

        {

            charArray[i] = (char) (charArray[i] ^ 20000);

        }

        System.out.println("加密或解密的结果如下:");

        System.err.println(new String(charArray));

    }

    public static void triangle(){

        int arr[][] = new int[10][];

        for (int i = 0; i < arr.length; i++)

        {

            arr[i] = new int[i+1];

            for (int j = 0; j <=i; j++)

            {

                if (i==0||j==0||j==i)

                {

                    arr[i][j] = 1;//两侧的数值均为1

                }else {

                    arr[i][j] = arr[i-1][j] + arr[i-1][j-1];//正上方的数值与其左上方的数值之和

                }

                System.out.print(arr[i][j] + "\t");

            }

            System.out.println();

        }

    }

}