Java基础练习题

**Java基础练习题**

### 一、基本语法####1.1 变量和数据类型* **变量定义**

java// int型变量int a =10;
// double型变量double b =3.14;
// boolean型变量boolean c = true;

* **常用数据类型**

java// byte型变量byte d =127;
// short型变量short e =32767;
// long型变量long f =2147483647L;
// float型变量float g =3.14F;

* **基本运算符**

javaint x =10;
int y =5;
System.out.println(x + y); // 输出15System.out.println(x - y); // 输出5System.out.println(x * y); // 输出50System.out.println(x / y); // 输出2

* **比较运算符**

javaint x =10;
int y =5;
System.out.println(x == y); // 输出falseSystem.out.println(x != y); // 输出trueSystem.out.println(x > y); // 输出trueSystem.out.println(x < y); // 输出false

* **逻辑运算符**

javaboolean x = true;
boolean y = false;
System.out.println(x && y); // 输出falseSystem.out.println(x || y); // 输出trueSystem.out.println(!x); // 输出false

####1.2 控制结构* **if语句**

javaint x =10;
if (x >5) {
 System.out.println("x大于5");
}

* **switch语句**

javaint x =3;
switch (x) {
 case1:
 System.out.println("x等于1");
 break;
 case2:
 System.out.println("x等于2");
 break;
 default:
 System.out.println("x不等于1或2");
}

* **for循环**

javafor (int i =0; i < 5; i++) {
 System.out.println(i);
}

* **while循环**

javaint i =0;
while (i < 5) {
 System.out.println(i);
 i++;
}

####1.3 数组* **数组定义**

javaint[] arr = new int[5];

* **数组元素访问**

javaint[] arr = {1,2,3,4,5};
System.out.println(arr[0]); // 输出1

* **数组长度**

javaint[] arr = {1,2,3,4,5};
System.out.println(arr.length); // 输出5

####1.4 方法* **方法定义**

javapublic class MethodExample {
 public static void main(String[] args) {
 System.out.println(add(10,20));
 }

 public static int add(int a, int b) {
 return a + b;
 }
}

* **方法参数**

javapublic class MethodExample {
 public static void main(String[] args) {
 System.out.println(greet("John"));
 }

 public static String greet(String name) {
 return "Hello, " + name;
 }
}

### 二、面向对象####2.1 类和对象* **类定义**

javapublic class Person {
 private String name;
 private int age;

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

 public void sayHello() {
 System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
 }
}

* **对象创建**

javapublic class Main {
 public static void main(String[] args) {
 Person person = new Person("John",30);
 person.sayHello();
 }
}

####2.2 构造函数* **无参构造函数**

javapublic class Person {
 private String name;
 private int age;

 public Person() {
 this.name = "Unknown";
 this.age =0;
 }

 // ...
}

* **有参构造函数**

javapublic class Person {
 private String name;
 private int age;

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

 // ...
}

####2.3 getter和setter* **getter**

javapublic class Person {
 private String name;

 public String getName() {
 return name;
 }
}

* **setter**

javapublic class Person {
 private String name;

 public void setName(String name) {
 this.name = name;
 }
}

####2.4 继承* **继承类定义**

javapublic class Animal {
 // ...
}

public class Dog extends Animal {
 // ...
}

* **继承方法**

javapublic class Animal {
 public void sound() {
 System.out.println("Animal makes a sound.");
 }
}

public class Dog extends Animal {
 @Override public void sound() {
 System.out.println("Dog barks.");
 }
}

####2.5 多态* **多态定义**

javapublic class Shape {
 // ...
}

public class Circle extends Shape {
 // ...
}

public class Rectangle extends Shape {
 // ...
}

* **多态方法**

javapublic class Shape {
 public void draw() {
 System.out.println("Drawing a shape.");
 }
}

public class Circle extends Shape {
 @Override public void draw() {
 System.out.println("Drawing a circle.");
 }
}

public class Rectangle extends Shape {
 @Override public void draw() {
 System.out.println("Drawing a rectangle.");
 }
}

### 三、异常####3.1 异常定义* **自定义异常**

javapublic class CustomException extends Exception {
 // ...
}

public class Main {
 public static void main(String[] args) {
 try {
 throw new CustomException();
 } catch (CustomException e) {
 System.out.println("Caught custom exception.");
 }
 }
}

* **预定义异常**

javapublic class Main {
 public static void main(String[] args) {
 try {
 int x =10 /0;
 } catch (ArithmeticException e) {
 System.out.println("Caught arithmetic exception.");
 }
 }
}

####3.2 异常处理* **try-catch块**

javapublic class Main {
 public static void main(String[] args) {
 try {
 int x =10 /0;
 } catch (ArithmeticException e) {
 System.out.println("Caught arithmetic exception.");
 }
 }
}

* **finally块**

javapublic class Main {
 public static void main(String[] args) {
 try {
 int x =10 /0;
 } catch (ArithmeticException e) {
 System.out.println("Caught arithmetic exception.");
 } finally {
 System.out.println("Finally block executed.");
 }
 }
}

####3.3 异常传递* **异常传递**

javapublic class Main {
 public static void main(String[] args) {
 try {
 method1();
 } catch (Exception e) {
 System.out.println("Caught exception in main.");
 }
 }

 public static void method1() throws Exception {
 throw new Exception();
 }
}

* **异常传递链**

javapublic class Main {
 public static void main(String[] args) {
 try {
 method2();
 } catch (Exception e) {
 System.out.println("Caught exception in main.");
 }
 }

 public static void method1() throws Exception {
 throw new Exception();
 }

 public static void method2() throws Exception {
 method1();
 }
}

### 四、集合####4.1 集合定义* **List接口**

javapublic class ListExample {
 public static void main(String[] args) {
 List list = new ArrayList<>();
 list.add("Apple");
 list.add("Banana");
 System.out.println(list);
 }
}

* **Set接口**

javapublic class SetExample {
 public static void main(String[] args) {
 Set set = new HashSet<>();
 set.add("Apple");
 set.add("Banana");
 System.out.println(set);
 }
}

####4.2 集合操作* **List集合**

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