*
 ***
*****
public class Test {
    public static void main(String[] args) {
        for(int i=1;i<=3;i++){
            for(int j=3-i;j>=1;j--)
                System.out.print(" ");
            for(int k=2*i-1;k>0;k--)
                System.out.print("*");
            System.out.println();
        }
    }
}

------解决方案--------------------
Java code

public class Main {
    public static void main(String[] args) {
        for(int i=4;i>=1;i--){
             StringBuilder builder=new StringBuilder("        ");
             for(int j=i;j<=8-i;j+=2){
                 builder.setCharAt(j, '*');
             }
             System.out.println(builder);
        }
    }

}

------解决方案--------------------
探讨

Java code
//文件名：xingxing.java
public class xingxing
{  
    public void san()
    {
        int i=0,j=0;
        for(i=0;i<4;i++)
        {                         
            for(j=5;j>i;j--)
            {
                System.out.print(" ");
            }
            
           for(int k=0;k<2*i-1;k++)
            {
               System.out.print("*");
            }
…


------解决方案--------------------
Java code


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class xingxing {

    public static void main(String[] args) {

        int lineNum = 0;
        boolean flag = true;
        StringBuffer stringBuffer = new StringBuffer("");

        while (flag) {
            try {
                System.out.print("请输入一个正整数:");
                lineNum = Integer.parseInt(new BufferedReader(new InputStreamReader(System.in))
                        .readLine());
                flag = false;
            } catch (IOException ioe) {
                ioe.printStackTrace();
                System.out.println("输入异常!!");
            } catch (NumberFormatException nume) {
                System.out.print("无法转换,请重新输入一个数:");
            }

            if (lineNum < 0) {
                flag = true;
                System.out.print("请输入一个正数:");
            }
        }

        // 组建基础空格串
        for (int i = 0; i < lineNum * 2; i++) {
            stringBuffer.append(" ");
        }

        for (int i = lineNum; i >= 1; i--) {
            StringBuilder builder = new StringBuilder(stringBuffer.toString());
            for (int j = i; j <= lineNum * 2 - i; j += 2) {
                builder.setCharAt(j, '*');
            }
            System.out.println(builder);
        }
    }
}