Week16 实训周20211216 - 《大数据专业-Java专业课》

代码1 Week16_3_1.java

package bigdata215.week16_3_1;
public class Week16_3_1 {
//和main方法并列的方法都必须是static   方法不调用不执行
    public static void main(String[] args) {        
        daYing();
        System.out.println("你好啊");
        daYing();
        System.out.println("今天不好啊");
        System.out.println("今天不好啊");
        System.out.println("你好啊");
        daYing();
        System.out.println("人间不值得");
        daYing(5,10);
        int sum=add(10, 15);
        System.out.println(sum);
    }
    public static void daYing(){
        for(int i=1;i<=3;i++){
            for(int j=1;j<=4;j++){
                System.out.print("*");                
            }
            System.out.println();
        }
    }
    public static void daYing(int a,int b){
        for(int i=1;i<=a;i++){
            for(int j=1;j<=b;j++){
                System.out.print("*");
            }
            System.out.println();
        }
    }
    public static int add(int a,int b){
        return a+b;
    } 
}

代码2 Week16_3_2.java

package bigdata215.week16_3_1;
public class Week16_3_2 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
          int sum = getSum(5);
          System.out.println(sum);
          int sum2=getSum2(5);
          System.out.println(sum2);
    }// 定义一个方法计算1+2+3+。。。。n
    public static int getSum(int n){
        int i=1;
        int sum=0;
        while(i<=n){
            sum=sum+i;
            i++;
        }
        return sum;
    } //递归 自己调用自己
    public static int getSum2(int n){
        if(n==1){
            return 1;
        }else{
            return getSum2(n-1)+n;
        }
    }
}

代码3 Week16_3_3.java

package bigdata215.week16_3_1;
//数组两种定义方法  数组的取值
public class Week16_3_3 {
    public static void main(String[] args) {
        int a=5;
        int b=6;
        int c=20;
        int[] arr1={1,5,8,6,8};//int类型数组的第一种定义  arr1数组名
        System.out.println(arr1);
        System.out.println(arr1[0]);//数组名[下标]
        System.out.println(arr1[4]);
        int[] arr2=new int[4];//数组的第二种定义  造出一个4个长度的int类型数组  默认值是0
        System.out.println(arr2[0]);
        System.out.println(arr2[1]);
        System.out.println(arr2[2]);
        System.out.println(arr2[3]);
        arr2[0]=88;
        arr2[1]=87;
        arr2[2]=8;
        arr2[3]=55;
        System.out.println(arr2[0]);
        System.out.println(arr2[1]);
        System.out.println(arr2[2]);
        System.out.println(arr2[3]);
        System.out.println(arr2[4]);//下标越界
        int arr3[]={1,5};//也行 
    }
}

代码4 Week16_3_4.java

package bigdata215.week16_3_1;
public class Week16_3_4 {
    public static void main(String[] args) {
        //各种类型的数组  数组的长度不可变
        int[] arr1={1,5,7};//静态初始化
        double[] arr2={1.2,4.6};
        String[] arr3={"hello","world"};
        char[] arr4={'a','b'};
        boolean[] arr5={true,false};
        Student s1 = new Student("张三", 5);
        Student s2= new Student("lisi", 8);
        //学生数组
        Student[] arr6={s1,s2};
        System.out.println(arr6[0].toString());//默认的toString()
        System.out.println(arr6[0]);
    }
}
class Student{
    String name;
    int age;
    public Student(String name,int age){
        this.name=name;
        this.age=age;
    }
    @Override
    public String toString() {
        return name+" "+age;
    }
}

代码5 Week16_3_5.java

package bigdata215.week16_3_1;
public class Week16_3_5 {//7  0-6 
    public static void main(String[] args) {
        int[] arr1={1,5,7,2,3,88,55,5,7,2,3,88,55,5,7,2,3,88,55,5,7,2,3,88,55,5,7,2,3,88,55};
        System.out.println(arr1[0]);
        System.out.println(arr1[1]);
        System.out.println(arr1[2]);//length
        System.out.println("=====================");//数组的遍历 正向遍历
        for(int i=0;i<arr1.length;i++){
            System.out.print(arr1[i]+" ");            
        }
    }
}

代码6 Week16_3_6.java 正序输出，倒序遍历输出，偶数遍历输出

package bigdata215.week16_3_1;
public class Week16_3_6 {
    public static void main(String[] args) {
        //定义方法来正序，倒序遍历
        int[] arr1={2,7,6,8};
            zhengXu(arr1);
        System.out.println();
        daoXu(arr1);
        System.out.println();
        scO(arr1);
    }
    //数组的正序输出方法
    public static void zhengXu(int[] arr){
        for(int i=0;i<arr.length;i++){
            System.out.print(arr[i]+" ");
        }
    }
    //数组的倒序输出方法
    public static void daoXu(int[] arr){
        for(int i=arr.length-1;i>=0;i--){
            System.out.print(arr[i]+" ");        
        }
    }
    //输出数组中的偶数方法
    public static void scO(int[] arr){
    for(int i=0;i<=arr.length-1;i++){
        if(arr[i]%2==0){
            System.out.println(arr[i]+" ");
        }
    }
}
}

下午Java课
Part1 编程找到这个数组的最大值以及最小值
1.1找到最大值

package bigdata215.week16_3_2;
public class Week16_3_1 {
    public static void main(String[] args) {
        int[] arr1={2,1,5,41,9,8};
        //编程找到这个数组的最大值
        int max=arr1[0];
        for(int i=1;i<arr1.length-1;i++){
            if(arr1[i]>max){
                max=arr1[i];
            }
            }
        System.out.println("最大值是："+max);
        }
    }

public class Week16_3_2{
    public static void main(String[] args){
        int[] arr1={23,11,5,41,9,8};
        int[] arr2={4,2,3,8};
        getMin(arr1);
        getMin(arr2);
    }
    public static void getMin(int[] arr){
        /*int[] arr1={23,11,5,41,9,8};*/
        int min=arr[0];
        for(int i=1;i<arr.length-1;i++){
            if(arr[i]<min){
                min=arr[i];
            }
        }
        System.out.println("最小值是"+min);
        }
}

冒泡排序