[The JavaSE] Logic Control

switch statement

• Depending on the value of the switch, it will perform the corresponding case statement. Break will encounter the end of the case statement.
• If the value of the switch is no matching case, will perform the default statements.
• We recommend a switch statement must bring the best default.

We see an example

public class Solution {
    public static void main(String[] args) {
        System.out.println("value="+switchit(4));
    }
    public static int switchit(int x) {
        int j=1;
        switch (x) {
            case 1:j++;
                break;
            case 2:j++;
                break;
            case 3:j++;
                break;
            case 4:j++;
                break;
            case 5:j++;
                break;
            default:j++;
                break;
        }
        return j+x;
    }
}

If you remove the break, we will look at

public class Solution {
    public static void main(String[] args) {
        System.out.println("value="+switchit(4));
    }
    public static int switchit(int x) {
        int j=1;
        switch (x) {
            case 1:j++;
            case 2:j++;
            case 3:j++;
            case 4:j++;
            case 5:j++;
            default:j++;
        }
        return j+x;
    }
}

The results and not the same as before, the reason is because they do not break when writing, case statement will in turn execute down, thus losing the multi-drop effect.
The while loop
Note:

1. And if similar, while the following statement {} can not write, but do not write when only support a statement. Plus recommendations or {}
2. And if similar, while {behind the proposals and while on the same line.
3. And if similar, do not write back while semicolon, or it may result in a cycle can not be performed correctly
   for the cycle
   to calculate 1! + 2! +3! +4! +5!

public class Solution {
    public static void main(String[] args) {
        int sum = 0;
        for(int i = 0;i <= 5;i++) {
            int temp = 1;
            for(int j = 1;j <= i;j++) {
                temp *= j;
            }
            sum += temp;
        }
        System.out.println("sum =" + sum);
    }
}

Notes (and while loops similar)

1. And if similar, for the following statement {} can not write, but do not write when only support a statement. Plus recommendations or {}
2. And if similar, for {behind the recommendation and while on the same line.
3. And if similar, for the back do not write a semicolon, or it may result in a cycle can not be executed properly
   do while loop

do {
   循环语句
}while(判断条件)

First execution loop, and then judges that the circulation condition.
More recommendation for or while

Output to the console

System.out.println(msg); // 输出一个字符串, 带换行
System.out.print(msg); // 输出一个字符串, 不带换行
System.out.printf(format, msg); // 格式化输出 

From the keyboard

- A character is read
directly System.in.read can be read into a character but needs with exception handling.

import java.io.IOException;
public class Solution {
    public static void main(String[] args) {
        try {
            System.out.print("Enter a Char:");
            char i = (char) System.in.read();
            System.out.println("your char is :"+i);
        } catch (IOException e) {
            System.out.println("exception");
        }
    }
}

Too much trouble, we do not recommend the use of

- Use Scanner to read the string / integer / floating point

import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入你的名字：");
        String name = sc.nextLine();
        System.out.println("请输入你的年龄：");
        int age = sc.nextInt();
        System.out.println("请输入你的工资：");
        float salary = sc.nextFloat();
        System.out.println("你的信息如下：");
        System.out.println("姓名："+name+"\n"+
        	"年龄："+age+"\n"+"工资："+salary);
        sc.close();
    }
}

• Scanner using N digital read cycle

import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double sum = 0.0;
        int num = 0;
        while (sc.hasNextDouble()) {
            double tmp = sc.nextDouble();
            sum += tmp;
            num++;
        }
        System.out.println("sum = " + sum);
        System.out.println("avg = " + sum / num);
        sc.close();
    }
}

Note: When entering multiple cycles of data, use ctrl + z to end the input (on Windows using the ctrl + z, Linux / Mac use + Ctrl
d)