java根据用户输入，输出指定的台阶，如何使用循环条件啊

import javax.swing.*;
import java.applet.Applet;
import java.awt.*;
public class MyApplet extends Applet {
    String userStr;
    public void init(){
        userStr = JOptionPane.showInputDialog("Enter no of step");
    }
    public void paint(Graphics graphics) {
        int x=70;
        int y=70;
        for(int i=1;i<=Integer.parseInt(userStr);i++){
            if (i==1){
                graphics.drawLine(10,10,70,10);// horizontal line
                graphics.drawLine(70,10,70,70);//vertical line
            }else{
                graphics.drawLine(x,y,x=70*i,y);
                graphics.drawLine(x,y,x=x,y=70*i);
            }
        }
    }
}

根据这里的变量。找规律。然后写for循环。

类似于下边，参照着改一下吧

class A extends Applet {
    // 起始点偏移
    int startPosX = 10;
    int startPosY = 10;
    // 输入的台阶数量
    int input = 10;
    // 每个台阶的宽高
    int perStepLen = 50;

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        int nowX = startPosX;
        int nowY = startPosY;
        for (int i = 0; i < input; i++) {
            g.drawLine(nowX, nowY, nowX += perStepLen, nowY);
            g.drawLine(nowX, nowY, perStepLen, nowY += perStepLen);
        }
    }
}