吴裕雄--天生自然 JAVA开发学习：方法

/** 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");
  }
}