Getting started with must-memorize code in java

Java is a widely used programming language with the characteristics of cross-platform, security, portability, multi-threading, etc., so it is widely used in various software development fields. When learning Java programming, there are some key concepts and codes that Java beginners must master.

1. Basic data types and variables

The basic data types of Java include byte, short, int, long, float, double, boolean and char. These data types are Java The basics of programming, you need to be familiar with their uses and features. In addition, learn how to declare, assign, and access variables.

public class Main {
public static void main(String[] args) {
byte b = 1;
short s = 2;
int i = 3;
long l = 4L;
float f = 5.0f;
double d = 6.0;
boolean bool = true;
char c = 'A';
}
}

2. Operators and expressions

Operators in Java include arithmetic operators, relational operators, logical operators, assignment operators, etc. Familiarity with the usage and precedence of these operators is fundamental to writing Java code.

public class Main {
public static void main(String[] args) {
int a = 10;
int b = 20;
int c = a + b;
int d = a * b;
int e = a > b ? 1 : 0;
}
}

3. Control statements

Control statements are statements used to control the execution flow of the program, including conditional statements (if, else, switch), loop statements (for , while, do-while) and jump statements (break, continue, return), etc. Mastering the use of these control statements can help you write more complex programs.

public class Main {
public static void main(String[] args) {
int i = 1;
while (i <= 10) {
System.out.println(i);
i++;
}
}
}

4, Arrays and Strings

An array in Java is a container used to store multiple data of the same type. Learning how to declare arrays, create arrays, access array elements, and manipulate arrays is an essential skill in Java programming. Also, the string is Another important data type in Java requires mastering the operation methods and techniques of strings.

public class Main {
public static void main(String[] args) {
int[] arr = {1, 2, 3, 4, 5};
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
String str = "Hello, World!";
System.out.println(str.length());
}
}

5. Object-oriented programming

Java is an object-oriented programming language, so understanding the basic concepts and principles of object-oriented programming is a must for Java beginners class. These concepts include classes, objects, inheritance, encapsulation, polymorphism, etc.

public class Main {
public static void main(String[] args) {
Animal dog = new Animal();
dog.eat();
Animal cat = new Cat();
cat.eat();
}
}
class Animal {
public void eat() {
System.out.println("Animal eating...");
}
}
class Cat extends Animal {
public void eat() {
System.out.println("Cat eating...");
}
}

6. Exception handling

In Java programming, exception handling is an important link. Learning how to handle exceptions can improve the robustness of your program. Exception handling mechanisms in Java include try-catch-finally statement, throws keyword, custom exception class, etc.

public class Main {
public static void main(String[] args) {
try {
int[] arr = new int[10];
for (int i = 0; i < arr.length; i++) {
arr[i] = 10;
}
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Array index out of bounds");
}
}

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