吴裕雄--天生自然 JAVA开发学习：方法

Posted 2021-12-16 tszr

/** 返回两个整型变量数据的较大值 */
public static int max(int num1, int num2) 
   int result;
   if (num1 > num2)
      result = num1;
   else
      result = num2;
 
   return result; 

public class TestMax 
   /** 主方法 */
   public static void main(String[] args) 
      int i = 5;
      int j = 2;
      int k = max(i, j);
      System.out.println( i + " 和 " + j + " 比较，最大值是：" + k);
   
 
   /** 返回两个整数变量较大的值 */
   public static int max(int num1, int num2) 
      int result;
      if (num1 > num2)
         result = num1;
      else
         result = num2;
 
      return result; 
   

public class TestVoidMethod 
  public static void main(String[] args) 
    printGrade(78.5);
  
 
  public static void printGrade(double score) 
    if (score >= 90.0) 
       System.out.println(‘A‘);
    
    else if (score >= 80.0) 
       System.out.println(‘B‘);
    
    else if (score >= 70.0) 
       System.out.println(‘C‘);
    
    else if (score >= 60.0) 
       System.out.println(‘D‘);
    
    else 
       System.out.println(‘F‘);
    
  

public static void nPrintln(String message, int n) 
  for (int i = 0; i < n; i++) 
    System.out.println(message);
  

public class TestPassByValue 
  public static void main(String[] args) 
    int num1 = 1;
    int num2 = 2;
 
    System.out.println("交换前 num1 的值为：" +
                        num1 + " ，num2 的值为：" + num2);
 
    // 调用swap方法
    swap(num1, num2);
    System.out.println("交换后 num1 的值为：" +
                       num1 + " ，num2 的值为：" + num2);
  
  /** 交换两个变量的方法 */
  public static void swap(int n1, int n2) 
    System.out.println("\\t进入 swap 方法");
    System.out.println("\\t\\t交换前 n1 的值为：" + n1
                         + "，n2 的值：" + n2);
    // 交换 n1 与 n2的值
    int temp = n1;
    n1 = n2;
    n2 = temp;
 
    System.out.println("\\t\\t交换后 n1 的值为 " + n1
                         + "，n2 的值：" + n2);
  

// 一个简单的构造函数
class MyClass 
  int x;
 
  // 以下是构造函数
  MyClass() 
    x = 10;
  

// 一个简单的构造函数
class MyClass 
  int x;
 
  // 以下是构造函数
  MyClass(int i ) 
    x = i;
  

public class ConsDemo 
  public static void main(String args[]) 
    MyClass t1 = new MyClass( 10 );
    MyClass t2 = new MyClass( 20 );
    System.out.println(t1.x + " " + t2.x);
  

public class VarargsDemo 
    public static void main(String args[]) 
        // 调用可变参数的方法
        printMax(34, 3, 3, 2, 56.5);
        printMax(new double[]1, 2, 3);
    
 
    public static void printMax( double... numbers) 
        if (numbers.length == 0) 
            System.out.println("No argument passed");
            return;
        
 
        double result = numbers[0];
 
        for (int i = 1; i <  numbers.length; i++)
            if (numbers[i] >  result) 
                result = numbers[i];
            
        
        System.out.println("The max value is " + result);
    

public class FinalizationDemo   
  public static void main(String[] args)   
    Cake c1 = new Cake(1);  
    Cake c2 = new Cake(2);  
    Cake c3 = new Cake(3);  
      
    c2 = c3 = null;  
    System.gc(); //调用Java垃圾收集器
    
  
 
class Cake extends Object   
  private int id;  
  public Cake(int id)   
    this.id = id;  
    System.out.println("Cake Object " + id + "is created");  
    
    
  protected void finalize() throws java.lang.Throwable   
    super.finalize();  
    System.out.println("Cake Object " + id + "is disposed");