Java 方法与调用

Java 方法与调用

• 方法定义

  /*
  修饰符  返回值类型 方法名（...）{
      //方法体
      return 返回值；
  }
   */
  public String test(){
      return "hello";
  }
  
  public void test1(){
      return;
  }
  
  public int max(int a,int b){
      int c = a>b?1:0;
      return c;
  }
  

• 静态方法调用

  public class Demo02 {
  
      public static void main(String[] args) {
          Student.say();
      }
      
  }
  
  public class Student {
  
      // 静态方法：static
      public static void say(){
          System.out.println("student is saying");
      }
  }
  
  //student is saying
  

• 非静态方法调用

  public class Demo02 {
      public static void main(String[] args) {
          //实例化这个类
          Student student = new Student();
          student.say();
      }
  }
  
  public class Student {
      // 非静态方法
      public void say(){
          System.out.println("student is saying");
      }
  }
  //student is saying
  

• static 方法是和类一起加载的，非静态方法是类实例化后才加载的。

• Java 都是值传递

  public static void main(String[] args) {
      int a  = 1;
      change(a);
      System.out.println(a);
  }
  
  //无返回值
  public static void change(int a){
     a = 10;
  }
  
  //1
  

• 引用传递

  public class Demo04 {
      //引用传递：对象，本质还是值传递
      public static void main(String[] args) {
          Person person = new Person();
          System.out.println(person.name);
  
          Demo04.change(person);
          System.out.println(person.name);
      }
  
      public static void change(Person person){
          person.name = "张三";
      }
  }
  
  //定义一个Person类，属性name
  class Person{
      String name;
  }
  
  //null
  张三