【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]");
    }
}

3.2

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());
    }
}

3.3

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);
    }
}

3.4

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");
    }
}

3.5-3.6

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));
    }
}

3.7

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() + " ");
    }
}

3.8

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));
    }
}

3.9

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);
    }
}

3.10

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));
    }
}

3.11-3.12

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));
        }
    }
}

3.13

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));
    }
}

3.14

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);
    }
}