【TIJ4】第三章全部习题

题目都相当简单没啥说的直接放代码就行了...

3.1

 package ex0301;
 //[3.1]使用“简短的”和正常的打印语句来写一个程序

 import static java.lang.System.out;
 public class Abbreviate
 {
     public static void main(String[] args)
     {
         System.out.println("Hello, world! [complete]");
         out.println("Hello, world! [abbreviate]");
     }
 }

3.1

3.2

 package ex0302;
 //[3.2]创建一个包含一个float域的类，并用这个类来展示别名机制
 class ShowByname
 {
     private float elem;
     public float getElem() { return elem; }
     public void setElem(float _elem) { elem = _elem; }
 }

 public class Byname
 {
     public static void main(String[] args)
     {
         ShowByname test1 = new ShowByname();
         test1.setElem(1.333f);
         System.out.println("test1.elem = " + test1.getElem());

         ShowByname test2 = test1;
         System.out.println("test2.elem = " + test2.getElem());

         //仅修改引用test2并观察
         test2.setElem(3.14159f);
         System.out.println("test1.elem = " + test1.getElem());
         System.out.println("test2.elem = " + test2.getElem());
     }
 }

3.2

3.3

 package ex0303;
 //[3.3]创建一个包含一个float域的类，并用这个方法来展示方法调用时的别名机制

 class ShowFunByname
 {
     public float elem = 3.14f;
 }

 public class FunByname
 {
     static void f(ShowFunByname test)
     {
         test.elem = 1.414f;
     }

     public static void main(String[] args)
     {
         ShowFunByname test = new ShowFunByname();
         System.out.println("1: elem = " + test.elem);

         f(test);
         System.out.println("2: elem = " + test.elem);
     }
 }

3.3

3.4

 package ex0304;

 //[3.4]编写一个计算速度的程序，它使用的距离和时间都是常量
 class CalVelocity
 {
     private final double distance = 100.0;
     private final double time = 3.5;
     public double getVelocity() { return distance/time; }
 }

 public class Velocity
 {
     public static void main(String[] args)
     {
         CalVelocity test = new CalVelocity();
         System.out.println(test.getVelocity()+"km/h");
     }
 }

3.4

3.5-3.6

 package ex030506;

 //[3.5]创建一个名为Dog的类，它包含两个String域:name和says.在main方法中,创建两个Dog对象.
 //一个名叫spot,叫声为“Ruff!”;另一个名为scruffy,叫声为"Wurf!".然后显示它们的名字和叫声.
 //[3.6]在练习5的基础上,创建一个新的Dog索引,并对其赋值为spot对象.测试用==和euqals()方法来比较所有引用的结果.

 class Dog
 {
     private String name;
     private String says;
     public Dog(String _name, String _says)
     {
         name=_name;
         says=_says;
     }

     public String getName() { return name; }
     public String getSays() { return says; }
 }

 public class TestEqual
 {
     public static void main(String[] args)
     {
         //[3.5]
         Dog dogA = new Dog("spot" , "Ruff!");
         Dog dogB = new Dog("scruffy" , "Wurf!");
         System.out.println("dogA's name is " + dogA.getName()+" and says "+dogA.getSays());
         System.out.println("dogB's name is " + dogB.getName()+" and says "+dogB.getSays());

         //[3.6]
         Dog dogindex = dogA;
         System.out.print(dogindex==dogA); System.out.println(dogindex.equals(dogA));
         System.out.print(dogA==dogB); System.out.println(dogA.equals(dogB));
         System.out.print(dogindex==dogB); System.out.println(dogindex.equals(dogB));
     }
 }

3.5-3.6

3.7

 package ex0307;
 //[0307]编写一个程序模拟随机扔硬币的结果

 class Coin
 {
     private boolean state;
     public boolean toss()
     {
         state=(Math.random() < 0.5);
         return state;
     }
 }
 public class TestCoin
 {
     public static void main(String[] args)
     {
         Coin onedollar = new Coin();
         for(int i = 0; i < 20; ++i)
             System.out.print(onedollar.toss() + " ");
     }
 }

3.7

3.8

 package ex0308;
 //[3.8]展示用十六进制和八进制计数法来操作long值,用Long.toBinaryString()来显示结果.

 public class TestOctHex
 {
     public static void main(String[] args)
     {
         long first = 256L;
         long second = 0256L;
         long third = 0x256L;

         System.out.println("first = " + Long.toBinaryString(first));
         System.out.println("second = " + Long.toBinaryString(second));
         System.out.println("third = " + Long.toBinaryString(third));
     }
 }

3.8

3.9

 package ex0309;
 //[3.9]分别显示用float和double指数计数法所能表示的最大和最小的数字

 public class ExpLimit
 {
     public static void main(String[] args)
     {
         double doublemax = Double.MAX_VALUE;
         double doublemin = Double.MIN_VALUE;
         float floatmax = Float.MAX_VALUE;
         float floatmin = Float.MIN_VALUE;

         System.out.println("doublemax = " + doublemax);
         System.out.println("doublemin = " + doublemin);
         System.out.println("floatmax = " + floatmax);
         System.out.println("floatmin = " + floatmin);
     }
 }

3.9

3.10

 package ex0310;
 //[3.10]编写一个具有两个常量值的程序,一个具有交替的二进制位1和0,其中最低有效位为0,另一个也具有交替的二进制位1和0,其中最低有效位为1.
 //取这两个值,用按位操作符以所有可能的方式结合运算它们,然后用Integer.toBinaryString()显示

 public class TestBitOperation
 {
     public static void main(String[] args)
     {
         int first = 0x2AA;
         int second =0x133;
         System.out.println("first = " + Integer.toBinaryString(first));
         System.out.println("sceond = " + Integer.toBinaryString(second));
         System.out.println("first & second = " + Integer.toBinaryString(first & second));
         System.out.println("first | second = " + Integer.toBinaryString(first | second));
         System.out.println("first ^ second = " + Integer.toBinaryString(first ^ second));
         System.out.println("~first = " + Integer.toBinaryString(~first));
         System.out.println("~sceond = " + Integer.toBinaryString(~second));
     }
 }

3.10

3.11-3.12

 package ex031112;
 //[3.11]以一个最高有效位为1的二进制数开始,用有符号右移操作符对其进行右移,直至所有的二进制位都被移出为止,每移一位都显示二进制字符串效果.
 //[3.12]以一个所有位都为1的二进制数字开始,先左移它,然后用无符号右移操作符对其进行右移,直至所有二进制位都移出为止,每移一位都要显示二进制字符串效果.

 public class TestBitShift
 {
     public static void main(String[] args)
     {
         //[3.11]
         int first = 0xF3A7;
         while(first != 0)
         {
             first >>= 1;
             System.out.println(Integer.toBinaryString(first));
         }

         //[3.12]
         int second = 0xFFFF;
         second <<= 1;
         System.out.println(Integer.toBinaryString(second));
         while(second != 0)
         {
             second >>= 1;
             System.out.println(Integer.toBinaryString(second));
         }
     }
 }

3.11-3.12

3.13

 package ex0313;
 //[3.13]编写一个方法,它以二进制形式显示char类型的值.使用多个不同的字符来展示它.

 class TestCharToBinaryString
 {
     public static String transform(char x)
     {
         return Integer.toBinaryString((int) x);
     }
 }

 public class CharToBinaryString
 {
     public static void main(String[] args)
     {
         char first = 'a';
         char second = '&';
         char third = '6';

         System.out.println("a: " + TestCharToBinaryString.transform(first));
         System.out.println("&: " + TestCharToBinaryString.transform(second));
         System.out.println("6: " + TestCharToBinaryString.transform(third));
     }
 }

3.13

3.14

 package ex0314;
 //[3.14]编写一个接收两个字符串参数的方法,用各种布尔值的比较关系来比较这两个字符串,然后把结构打印出来.
 //做==和!=比较的同事,用equals()作测试.在main()里面用几个不同的字符串对象调用这个方法

 import java.lang.String;
 class StringCompare
 {
     public static void go(String first , String second)
     {
         System.out.println(first + " compareTo " + second + " : " + (first.compareTo(second)));
         System.out.println(first + " != " + second + " : " + first != second);
         System.out.println(first + " == " + second + " : " + first == second);
         System.out.println(first + " equals " + second + " : " + first.equals(second));
         System.out.println("");
     }
 }

 public class TestStringCompare
 {
     public static void main(String[] args)
     {
         String first = new String("Good");
         String second = new String("Bad");
         String third = first;

         StringCompare.go(first, second);
         StringCompare.go(third, second);
         StringCompare.go(first, third);
     }
 }

3.14