java基础必背代码

1. 变量和数据类型
java
int number = 10;
double pi = 3.14;
boolean isTrue = false;
String name = "John";
2. 控制流
java
if (condition) {
// 代码块
} else {
// 代码块
}
while (condition) {
// 代码块
}
do {
// 代码块
} while (condition);
for (int i = 0; i < 10; i++) {
// 代码块
}
3. 数组
java
int[] numbers = {1, 2, 3, 4, 5};
String[] names = {"John", "Mary", "Bob"};
4. 方法
java
public void printName() {
System.out.println("My name is John");
}
5. 类和对象
java
class Person {
private String name;
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
6. 输入和输出
java
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
System.out.println("Output: " + input);
7. 异常处理
java
try {
// 代码块
} catch (Exception e) {
// 异常处理代码块
}
8. 集合
java
List numbers = new ArrayList<>();
numbers.add(1);
numbers.add(2);
numbers.add(3);
Set names = new HashSet<>();
names.add("John");
names.add("Mary");
names.add("Bob");
Map ages = new HashMap<>();
ages.put("John", 30);
ages.put("Mary", 25);
ages.put("Bob", 40);
9. 线程
java
class MyThread extends Thread {
@Override
public void run() {
// 线程代码块
}
}