07-30 数组

一维数组定义

        int[] array1=new int[10];        Scanner scanner=new Scanner(System.in);        for (int i = 0; i < array1.length; i++) {            array1[i]=scanner.nextInt();        }        for (int j = 0; j < array1.length; j++) {            System.out.println(array1[j]);        }        int[] array2={1,2,3,4,5,6,7};        for (int j = 0; j < 7; j++) {            System.out.println(array2[j]);        }

求平均值

        double[] scores=new double[5];        Scanner scanner=new Scanner(System.in);        double sum=0;        for (int i = 0; i < scores.length; i++) {            System.out.println("请输入数据:");            scores[i]=scanner.nextDouble();            sum=sum+scores[i];        }        System.out.println("平均分是"+sum/5);

冒泡排序

       int[] array={52,75,73,42,36,92};        for (int i = 0; i < array.length-1; i++) {            for (int j = 0; j < array.length-i-1; j++) {                int temp=0;                if(array[j]>array[j+1]){                    temp=array[j];                    array[j]=array[j+1];                    array[j+1]=temp;                }            }        }        //Arrays.sort(array);（排序方法）        for (int i = 0; i < array.length; i++) {            System.out.println(array[i]);        }

数组截取

int[] array={52,75,73,42,36,92};int[] array1=Arrays.copyOfRange(array, 1,4);for (int i = 0; i < array1.length; i++) {            System.out.println(array1[i]);        }

数组复制

int[] array={52,75,73,42,36,92};int[] array2=new int[10];System.arraycopy(array, 1, array2, 1, 4);for (int i = 0; i < array2.length; i++) {            System.out.println(array2[i]);}

二维数组定义

        int[][] array=new int[3][];        array[0]=new int[]{1,2,3,4,5};        System.out.println(array[0][1]);        int[][] array1=new int [2][3];        array1[1]=new int[]{1,2,3,4,5};         System.out.println(array1[1][4]);        int[][] array2={{1,2,3},{4,5,6},{7,8,9}};        System.out.println(array2[1][2]);

判断邮箱地址

        System.out.println("请输入邮箱地址:");        Scanner scanner=new Scanner(System.in);        String email=scanner.next();        if(email.contains("@")){            int index=email.indexOf("@");            String start=email.substring(0, index);            boolean isLetterOrNum=true;            for (int i = 0; i < start.length(); i++) {                char ch=start.charAt(i);                if(!Character.isLetterOrDigit(ch)){                    break;                }            }            if(isLetterOrNum==false){                System.out.println("起始不是字母或数字!");            }            if(email.contains(".")){                int index1=email.lastIndexOf(".");                String center=email.substring(index+1, index1);                boolean isNumOrLetter=true;                for (int i = 0; i < center.length(); i++) {                    char ch1=center.charAt(i);                    if(!Character.isDigit(ch1)){                        break;                    }                }                if(isNumOrLetter==false){                    System.out.println("中间不是数字!");                }            }else{                System.out.println("缺少.符号!");            }            boolean end=false;            if(email.endsWith(".com")||email.endsWith(".cn")){                end=true;                System.out.println("邮箱格式正确!");            }else{                System.out.println("结尾格式格式错误!");            }        }else{            System.out.println("缺少@符号!");        }

字符串切换大小写

        String str="asdQWQzxc";        String s="";        for (int i = 0; i < str.length(); i++) {            char c=str.charAt(i);            boolean islower=Character.isLowerCase(c);            if(islower){                c=Character.toUpperCase(c);            }else{                c=Character.toLowerCase(c);            }            s=s+c;        }        System.out.println(s);

随机产生10个两位数，冒泡排序，从小到大输出

        Random ran=new Random();        int[] array=new int[10];        for (int i = 0; i < array.length; i++) {            array[i]=ran.nextInt(90)+10;            System.out.print(array[i]+" ");        }        System.out.println();        Arrays.sort(array);        System.out.println(Arrays.toString(array));

输入一个四维数组，求正，副对角线上数的乘积

        int[][] array=new int[4][4];        Random ran=new Random();        for (int i = 0; i < array.length; i++) {            for (int j = 0; j < array.length; j++) {                array[i][j]=ran.nextInt(10);                System.out.print(array[i][j]+"\t");            }            System.out.println();        }        int temp1=1;        int temp2=1;        for (int i = 0; i < array.length; i++) {            temp1=temp1*array[i][i];  //array[i][i]可以直接取值             temp2=temp2*array[i][4-i-1];        }        System.out.println("主对角线乘机为:"+temp1);        System.out.println("副对角线乘机为:"+temp2);