Java - 基础代码

package base;

public class base01 {
    public static void main(String[] args) {

        System.out.println("hello");
    }
}

package base;

public class base02 {
    public static void main(String[] args) {
        int a = 100;
        int b = 200;
        byte c = 100;
        byte d = 100;
        System.out.println(a+b);
        System.out.println(c+d);

//       类型强转
        a = (byte) a;
        b = (byte) b;
        System.out.println(a);
        System.out.println(b);
    }
}

package base;

public class base03 {
    public static void main(String[] args) {
        int a = 12;
        {
            int b = 2;
            System.out.println(a);
            System.out.println(b);
//            赋值运算符
            b += a;
            System.out.println(b);
        }
//        System.out.println(b);
//        作用域
        int x, y, z, k;
        x = y = z = 10;
//        错误写法
//        int x = y = z = 10;
    }
}

package base;

public class base04 {
    public static void main(String[] args) {
        String macbook = "macbook";
        double macsize = 13.3;
        double macprice = 19999.99;
        String macconfig = "i5+4GB+500G";
        int maccount = 5;
        System.out.println("-------------------商城库存清单-----------------------");
        System.out.println("品牌型号        尺寸      价格      配置          库存数");
        System.out.println(macbook+"    "+macsize+"     "+macprice+"    "+macconfig+"   "+maccount);
    }
}

package base;

public class base05 {
    public static void main(String[] args) {
        int a = 10;
        if (a <10) {
            a++;
            System.out.println(a);
        }
        if (a %2 == 0 ) {
            System.out.println("a可以被2整除");
        }else {
            System.out.println("a不可以被2整除!");
        }
    }
}

package base;

public class base06 {
    public static void main(String[] args) {
        int grade = 75;
        if (grade >= 90) {
            System.out.println("优");
        }else if (grade >= 75) {
            System.out.println("良");
        }else if (grade >= 60) {
            System.out.println("及格");
        }else {
            System.out.println("不及格");
        }
    }
}

package base;

public class base07 {
    public static void main(String[] args) {
        int finger = 5;
        switch (finger){
            case 1:
                System.out.println("大拇指");
                break;
            case 2:
                System.out.println("食指");
                break;
            case 3:
                System.out.println("中指");
                break;
            case 4:
                System.out.println("无名指");
                break;
            case 5:
                System.out.println("小拇指");
                break;
            default:
                System.out.println("没有");
                break;
        }
        int week = 6;
        switch (week){
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
                System.out.println("上班");
                break;
            case 6:
            case 7:
                System.out.println("休息");
                break;

        }
    }
}

package base;

public class base08 {
    public static void main(String[] args) {
        int a = 0;
        while (a < 10){
            System.out.println("$"+a);
            a ++;
        }
        System.out.println("a现在的值为："+a);
//      while循环
        do {
            System.out.println(a);
            a = a+2;
        }while (a < 20);
        System.out.println("a现在的值为："+a);
//        dowhile循环
        for (int i = 5; i < 10; i++) {
            System.out.println(a);
            a++;
        }
        System.out.println("a现在的值为："+a);
//        for循环
        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < i; j++) {
                System.out.print("*");
            }
            System.out.print("\n");
        }
//        循环嵌套  打印三角形

        int sum = 0;
        for (int i = 0; i < 10; i++) {
            if (i % 2 == 0) {
                continue;
            }
            sum += i;
        }
        System.out.println(sum);
//        continue  终止本次循环继续下次循环
    }
}

package base;

import java.util.Random;
import java.util.Scanner;

public class base09 {
    public static void main(String[] args) {
        int i = 1;
        int randomnumber = new Random().nextInt(10);
        System.out.println("随机数已产生");
        System.out.println("请输入你猜的数字:");
        Scanner sc = new Scanner(System.in);
        int enternumber = sc.nextInt();
        while (enternumber != randomnumber){
            i++;
            if (enternumber > randomnumber) {
                System.out.println("你猜大了");
            }else{
                System.out.println("你猜小了");
            }
            enternumber = sc.nextInt();
        }
        System.out.println("恭喜你猜对了！你一共猜了"+i+"次");
    }
}

package base;

public class base10 {
    public static void main(String[] args) {
        recttangle(8,3);
        System.out.println(area(8,3));
//        调用方法
    }
    public static void  recttangle (int x,int y) {
//        画矩形方法
        for (int i = 0; i < y; i++) {
            for (int j = 0; j < x; j++) {
                System.out.print("*");
            }
            System.out.print("\n");
        }
    }
    public static int area(int x,int y) {
//        计算面积
        int temp = x*y;
        return temp;
    }
}

package base;

public class base11 {
    public static void main(String[] args) {
        int sum1 = add(1,2);
        int sum2 = add(1,2,3);
        double sum3 = add(1.4,3.1);
        System.out.println(sum1+"---"+sum2+"----"+sum3);
    }
    public static int add ( int x, int y){
        System.out.println("重载方法1");
        return x + y;
    }
    public static int add(int x ,int y,int z){
        System.out.println("重载方法2");
        return x + y + z;
    }
    public static double add(double x, double y){
        System.out.println("重载方法3");
        return x+y;
    }
}

package base;

public class base12 {
    public static void main(String[] args) {
        int [] arr = new int[4];
        arr[0] = 1;
        arr[2] = 2;
        arr[3] = 3;
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
    }
}

package base;

public class base13 {
    public static void main(String[] args) {
        int[] arr = {10,2,3,4,0};
        System.out.println(getmax(arr));
    }
    static int getmax(int[] arr){
//        取最大值
        int max = arr[0];
        for (int i = 0; i < arr.length; i++) {
            if (max < arr[i]){
                max = arr[i];
            }
        }
        return max;
    }
}

package base;


public class base14 {
    public static void main(String[] args) {
//冒泡排序
        int[] arr = {2,9,6,1,64,5,12};
        printarry(arr);
        System.out.println("初始数组");
        bubble(arr);
    }
    public static void printarry(int[] arr){
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+"/");
        }
    }
    public static void bubble(int[] arr){
        for (int i = 0; i < arr.length-1; i++) {
            for (int j = 0; j < arr.length-i-1; j++)
                if (arr[j] < arr[j + 1]) {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
            System.out.print("这是第"+i+1+"次排序");
            printarry(arr);
            System.out.print("\n");
        }
    }
}

来源：CSDN

作者：duzishivip

链接：https://blog.csdn.net/duzishivip/article/details/103734376