双重循环

n  |----若有3个班级各4名学员参赛，如何计算每个班级参赛学员的平均分？

|-----不用数组，用3个变量+多重循环（乘法）

|----打印一个简单矩形

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            for(int i=1;i<=5;i++){                  //行数                  for(int j=1;j<=20;j++){                       System.out.print("*");                  }                  System.out.println();//换行            }       }

|----打印直角三角形

publicstaticvoid main(String[] args) {         // TODO Auto-generated method stub         Scanner sc=new Scanner(System.in);//扫描仪         System.out.println("请输入三角形行数：");         int rows=sc.nextInt();         for(int i=1;i<=rows;i++){             //打印的行数             //每行显示的*号，规律             for(int j=1;j<=2*i-1;j++){                 System.out.print("*");             }             System.out.println();         }     }

|----现场编程 ：倒直角三角形

|----规律：每行少一个！

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            Scanner sc=new Scanner(System.in);            System.out.println("请输入行数：");            int rows=sc.nextInt();            for(int i=1;i<=rows;i++){                  //行数                  for(int j=1;j<=rows-i+1;j++){                       System.out.print("*");                  }                  System.out.println();            }       }

 |------打印等腰三角形

|-----1：占位置  2：1，3，5，7

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            Scanner sc=new Scanner(System.in);            System.out.println("请输入等腰三角形的行数:");            int rows=sc.nextInt();            for(int i=1;i<=rows;i++){                  //占位  倒直角三角形  规律                  for(int j=1;j<=rows-i;j++){                       System.out.print(" ");                  }                  for(int k=1;k<=2*i-1;k++){                       if(k==1||k==2*i-1){                             System.out.print("*");                       }else{                             System.out.print(" ");                       }                  }                  System.out.println();            }       }

|---打印九九乘法表

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            for(int i=1;i<=9;i++){                  //行数                  for(int j=1;j<=i;j++){                       System.out.print(i+"X"+j+"="+(i*j)+"\t");                  }                  System.out.println();//换行            }       }

|-----结合等腰和九九乘法表  试着打印一个菱形，不能输入偶数？17  7 把菱形进行缕空？

|------分成上部份和下部份

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            Scanner sc=new Scanner(System.in);            System.out.println("请输入菱形的行数：");            int rows=sc.nextInt();            while(rows%2==0){                  System.out.println("请输入菱形的行数：");                  rows=sc.nextInt();            }            //拆分成两部份            //打印上部份            int uprow=(rows+1)/2;            for(int i=1;i<=uprow;i++){                  //占位                  for(int j=1;j<=uprow-i;j++){                       System.out.print(" ");                  }                  for(int k=1;k<=2*i-1;k++){                       //System.out.print("*");                       if(k==1||k==2*i-1){                             System.out.print("*");                       }else{                             System.out.print(" ");                       }                  }                  System.out.println();            }            //打印下部份            int downrow=rows-uprow;            for(int i=downrow;i>=1;i--){                  //占位                  for(int j=1;j<=downrow-i+1;j++){                       System.out.print(" ");                  }                  for(int k=1;k<=2*i-1;k++){                       if(k==1||k==2*i-1){                             System.out.print("*");                       }else{                             System.out.print(" ");                       }                  }                  System.out.println();             }       }

n  |-----使用continue统计大于85分的学员人数

|-----break用在多循环中

n  |----有5家衣服专卖店，每家最多购买3件。用户可以选择离开，可以买衣服

n  最后打印总共买了几件衣服   用break来实现？

|---1：外层循环有5次

|---2：内层控制3次  用户可以选择离开（break），可以买衣服

|----3：最后再统计买了多少件衣服？

for(){do{}while();}

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            Scanner sc=new Scanner(System.in);            int count=0;            String flag="n";//标志位            for(int i=0;i<5;i++){                  System.out.println("欢迎进入第"+(i+1)+"家专卖店:");                  do{                       System.out.println("要离开吗?(y/n)");                       flag=sc.next();                       if(flag.equals("y")){                             break;                       }                       System.out.println("买一件衣服！");                       count++;                  }while(flag.equals("n"));            }            System.out.println("总共买了"+count+"件衣服！");       }

publicstaticvoid main(String[] args) {            // TODO Auto-generated method stub            Scanner sc=new Scanner(System.in);            int count=0;            int sum=0;            String flag="n";//标志位            for(int i=0;i<5;i++){                  count=0;//i执行1次，那么count清零                  System.out.println("欢迎进入第"+(i+1)+"家专卖店:");                  do{                       System.out.println("要离开吗?(y/n)");                       flag=sc.next();                       if(flag.equals("y")){                             sum+=count;                             break;//输入y退出                       }                       System.out.println("买一件衣服！");                       count++;                       if(count>=3){                             sum+=count;                             break;                       }                  }while(flag.equals("n"));            }            System.out.println("总共买了"+sum+"件衣服！");       }