This article introduces the basic concepts and structures of Java programming. It begins with an introduction to variables and data types, then discusses operators and expressions, as well as control flow processes. Second, it explains methods and classes, then introduces input and output operations. Finally, the article demonstrates the application of these concepts through a practical example of a salary calculator.

Think like a programmer: Master the basics of Java

1. Variables and data types

Java uses variables to store information. Each variable has a specific data type that indicates the type of value it can store. For example:

int age = 30; // 存储整数
String name = "John"; // 存储字符串
double balance = 100.50; // 存储小数

2. Operators and expressions

operators are used to perform operations on variables. Expressions combine operators with variables or values:

int sum = age   10; // 加法操作符
boolean isAdult = age >= 18; // 关系操作符
double discount = balance * 0.1; // 乘法操作符

3. Control flow

Control flow statements are used to control the execution flow of the program:

if (isAdult) {
    System.out.println("You are an adult.");
} else {
    System.out.println("You are not an adult.");
}

for (int i = 0; i 
4. Methods and Classes
Methods are reusable blocks of code that perform specific tasks. Classes are blueprints for objects. They define the state and behavior of the object: 
class Person {
    private int age;
    private String name;

    public Person(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public String getName() {
        return name;
    }
}
5. Input and Output
Java provides methods for reading input from the console and writing output to it:
Scanner input = new Scanner(System.in); // 读取输入
int inputAge = input.nextInt();

System.out.println("Your age is: "   inputAge); // 写入输出
Practical case: Salary Calculator
import java.util.Scanner;

public class SalaryCalculator {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // 输入小时数和时薪
        System.out.println("Enter the number of hours worked:");
        int hoursWorked = input.nextInt();

        System.out.println("Enter the hourly pay rate:");
        double hourlyRate = input.nextDouble();

        // 计算工资
        double grossSalary = hoursWorked * hourlyRate;

        // 输出工资
        System.out.println("Your gross salary is: "   grossSalary);
    }
}