Question

用java编写菱形

给代码给注释

Answer 1

for(i=1;i<=4;i++)

{

这个小的for是打印每一行前边的空格

for(j=1;j<=4-i;j++)

System.out.print(" ");

这个是打印星星的

for(j=1;j<=2*i-1;j++)

System.out.print("*");

这个是打印完一行的换行

System.out.println("");

}

下边的是一样的  只不过每一行的空格和星星数   和上边是翻过来的

for(i=1;i<=3;i++)

{

for(j=1;j<=i;j++)

System.out.print(" ");

for(j=1;j<=7-2*i;j++)

System.out.print("*");

System.out.println("");

}

java.sql.SQLException: 无效的列索引

无效的列索引

at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111)

at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:145)

at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:207)

atoracle.jdbc.driver.OraclePreparedStatement.setStringInternal(OraclePreparedStatement.java:5328)

atoracle.jdbc.driver.OraclePreparedStatement.setString(OraclePreparedStatement.java:5320)

at untitled5.addreader1.validID(addreader1.java:128)

at untitled5.addreader1.jButton1_actionPerformed(addreader1.java:97)

at untitled5.addreader1_jButton1_actionAdapter.actionPerformed(addreader1.java:175)

at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)

at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)

at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)

at javax.swing.DefaultButtonModel.setPressed(Unknown Source)

at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)

at java.awt.Component.processMouseEvent(Unknown Source)

at javax.swing.JComponent.processMouseEvent(Unknown Source)

at java.awt.Component.processEvent(Unknown Source)

at java.awt.Container.processEvent(Unknown Source)

at java.awt.Component.dispatchEventImpl(Unknown Source)

at java.awt.Container.dispatchEventImpl(Unknown Source)

at java.awt.Component.dispatchEvent(Unknown Source)

at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)

at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source

at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)

at java.awt.Container.dispatchEventImpl(Unknown Source)

at java.awt.Window.dispatchEventImpl(Unknown Source)

at java.awt.Component.dispatchEvent(Unknown Source)

at java.awt.EventQueue.dispatchEvent(Unknown Source)

at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.run(Unknown Source)

代码：String driverName = "oracle.jdbc.OracleDriver";

Driver driver = (Driver) Class.forName(driverName).newInstance();

//连接数据库

Connection con = DriverManager.getConnection(

"jdbc:oracle:thin:@LONG:1521:orcl", "sysman", "tongfang");

PreparedStatement pstmt = con.prepareStatement(

" insert into reader values(?)");

pstmt.setString(1, str1);

pstmt.setString(2,str2);

pstmt.setString(3,str3);

pstmt.setString(4,str4);

ResultSet res = pstmt.executeQuery();

Answer 2

int i,j;

总共2个大的for循环 里边有小的 对吧
第一个大的for是打印菱形的上半部分
for(i=1;i<=4;i++)
{
这个小的for是打印每一行前边的空格
for(j=1;j<=4-i;j++)
System.out.print(" ");
这个是打印星星的
for(j=1;j<=2*i-1;j++)
System.out.print("*");
这个是打印完一行的换行
System.out.println("");
}
下边的是一样的 只不过每一行的空格和星星数 和上边是翻过来的
for(i=1;i<=3;i++)
{
for(j=1;j<=i;j++)
System.out.print(" ");
for(j=1;j<=7-2*i;j++)
System.out.print("*");
System.out.println("");
}

追问

那个i,j可以理解成行和列吗

追答

2个大的循环控制的是行
中间2个小的循环控制的要打印的东西

Answer 3

这组程序可以实现很多种图形，先做出图案，根据坐标做出绝对值，空心菱形、三角形，都可以制作，我也是新手，欢迎采纳

Answer 4

参考下面主要代码：
public static void draw()
{
int n=10;
for(int i=1;i<=n;i++)//控制行数

{
for(int k=n-1;k>=i;k--)//打印空格
{
System.out.print(" ");
}
for(int j=1;j<=2*i-1;j++)//打印*
{
System.out.print("*");
}
System.out.println();
}
for(int i=n-1;i>=1;i--)

{
for(int k=i;k<=n-1;k++)
{
System.out.print(" ");
}
for(int j=1;j<=2*i-1;j++)
{
System.out.print("*");
}
System.out.println();
}
}

Answer 5

		for(int m=-8;m<=8;m=m+2) {
			for(int j=1;j<=(Math.abs(m))/2;j++) {
				System.out.print(" ");
			}
			for(int j=1;j<=9-Math.abs(m);j++) {
				System.out.print("*");
			}
			for(int j=1;j<=(Math.abs(m)-1)/2;j++){
				System.out.print(" ");
			}
			System.out.println();
		}