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");

  }

}