题目都相当简单没啥说的直接放代码就行了...
3.1
1 package ex0301;
2 //[3.1]使用“简短的”和正常的打印语句来写一个程序
3
4 import static java.lang.System.out;
5 public class Abbreviate
6 {
7 public static void main(String[] args)
8 {
9 System.out.println("Hello, world! [complete]");
10 out.println("Hello, world! [abbreviate]");
11 }
12 }
3.1
3.2
1 package ex0302;
2 //[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
3 class ShowByname
4 {
5 private float elem;
6 public float getElem() { return elem; }
7 public void setElem(float _elem) { elem = _elem; }
8 }
9
10 public class Byname
11 {
12 public static void main(String[] args)
13 {
14 ShowByname test1 = new ShowByname();
15 test1.setElem(1.333f);
16 System.out.println("test1.elem = " + test1.getElem());
17
18 ShowByname test2 = test1;
19 System.out.println("test2.elem = " + test2.getElem());
20
21 //仅修改引用test2并观察
22 test2.setElem(3.14159f);
23 System.out.println("test1.elem = " + test1.getElem());
24 System.out.println("test2.elem = " + test2.getElem());
25 }
26 }
3.2
3.3
1 package ex0303;
2 //[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
3
4 class ShowFunByname
5 {
6 public float elem = 3.14f;
7 }
8
9 public class FunByname
10 {
11 static void f(ShowFunByname test)
12 {
13 test.elem = 1.414f;
14 }
15
16 public static void main(String[] args)
17 {
18 ShowFunByname test = new ShowFunByname();
19 System.out.println("1: elem = " + test.elem);
20
21 f(test);
22 System.out.println("2: elem = " + test.elem);
23 }
24 }
3.3
3.4
1 package ex0304;
2
3 //[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
4 class CalVelocity
5 {
6 private final double distance = 100.0;
7 private final double time = 3.5;
8 public double getVelocity() { return distance/time; }
9 }
10
11 public class Velocity
12 {
13 public static void main(String[] args)
14 {
15 CalVelocity test = new CalVelocity();
16 System.out.println(test.getVelocity()+"km/h");
17 }
18 }
3.4
3.5-3.6
1 package ex030506;
2
3 //[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.
4 //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.
5 //[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.
6
7 class Dog
8 {
9 private String name;
10 private String says;
11 public Dog(String _name, String _says)
12 {
13 name=_name;
14 says=_says;
15 }
16
17 public String getName() { return name; }
18 public String getSays() { return says; }
19 }
20
21 public class TestEqual
22 {
23 public static void main(String[] args)
24 {
25 //[3.5]
26 Dog dogA = new Dog("spot" , "Ruff!");
27 Dog dogB = new Dog("scruffy" , "Wurf!");
28 System.out.println("dogA‘s name is " + dogA.getName()+" and says "+dogA.getSays());
29 System.out.println("dogB‘s name is " + dogB.getName()+" and says "+dogB.getSays());
30
31 //[3.6]
32 Dog dogindex = dogA;
33 System.out.print(dogindex==dogA); System.out.println(dogindex.equals(dogA));
34 System.out.print(dogA==dogB); System.out.println(dogA.equals(dogB));
35 System.out.print(dogindex==dogB); System.out.println(dogindex.equals(dogB));
36 }
37 }
3.5-3.6
3.7
1 package ex0307;
2 //[0307]编写一个程序模拟随机扔硬币的结果
3
4 class Coin
5 {
6 private boolean state;
7 public boolean toss()
8 {
9 state=(Math.random() < 0.5);
10 return state;
11 }
12 }
13 public class TestCoin
14 {
15 public static void main(String[] args)
16 {
17 Coin onedollar = new Coin();
18 for(int i = 0; i < 20; ++i)
19 System.out.print(onedollar.toss() + " ");
20 }
21 }
3.7
3.8
1 package ex0308;
2 //[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.
3
4 public class TestOctHex
5 {
6 public static void main(String[] args)
7 {
8 long first = 256L;
9 long second = 0256L;
10 long third = 0x256L;
11
12 System.out.println("first = " + Long.toBinaryString(first));
13 System.out.println("second = " + Long.toBinaryString(second));
14 System.out.println("third = " + Long.toBinaryString(third));
15 }
16 }
3.8
3.9
1 package ex0309;
2 //[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
3
4 public class ExpLimit
5 {
6 public static void main(String[] args)
7 {
8 double doublemax = Double.MAX_VALUE;
9 double doublemin = Double.MIN_VALUE;
10 float floatmax = Float.MAX_VALUE;
11 float floatmin = Float.MIN_VALUE;
12
13 System.out.println("doublemax = " + doublemax);
14 System.out.println("doublemin = " + doublemin);
15 System.out.println("floatmax = " + floatmax);
16 System.out.println("floatmin = " + floatmin);
17 }
18 }
3.9
3.10
1 package ex0310;
2 //[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.
3 //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
4
5 public class TestBitOperation
6 {
7 public static void main(String[] args)
8 {
9 int first = 0x2AA;
10 int second =0x133;
11 System.out.println("first = " + Integer.toBinaryString(first));
12 System.out.println("sceond = " + Integer.toBinaryString(second));
13 System.out.println("first & second = " + Integer.toBinaryString(first & second));
14 System.out.println("first | second = " + Integer.toBinaryString(first | second));
15 System.out.println("first ^ second = " + Integer.toBinaryString(first ^ second));
16 System.out.println("~first = " + Integer.toBinaryString(~first));
17 System.out.println("~sceond = " + Integer.toBinaryString(~second));
18 }
19 }
3.10
3.11-3.12
1 package ex031112;
2 //[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 //[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.
4
5 public class TestBitShift
6 {
7 public static void main(String[] args)
8 {
9 //[3.11]
10 int first = 0xF3A7;
11 while(first != 0)
12 {
13 first >>= 1;
14 System.out.println(Integer.toBinaryString(first));
15 }
16
17 //[3.12]
18 int second = 0xFFFF;
19 second <<= 1;
20 System.out.println(Integer.toBinaryString(second));
21 while(second != 0)
22 {
23 second >>= 1;
24 System.out.println(Integer.toBinaryString(second));
25 }
26 }
27 }
3.11-3.12
3.13
1 package ex0313;
2 //[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.
3
4 class TestCharToBinaryString
5 {
6 public static String transform(char x)
7 {
8 return Integer.toBinaryString((int) x);
9 }
10 }
11
12 public class CharToBinaryString
13 {
14 public static void main(String[] args)
15 {
16 char first = ‘a‘;
17 char second = ‘&‘;
18 char third = ‘6‘;
19
20 System.out.println("a: " + TestCharToBinaryString.transform(first));
21 System.out.println("&: " + TestCharToBinaryString.transform(second));
22 System.out.println("6: " + TestCharToBinaryString.transform(third));
23 }
24 }
3.13
3.14
1 package ex0314;
2 //[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.
3 //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
4
5 import java.lang.String;
6 class StringCompare
7 {
8 public static void go(String first , String second)
9 {
10 System.out.println(first + " compareTo " + second + " : " + (first.compareTo(second)));
11 System.out.println(first + " != " + second + " : " + first != second);
12 System.out.println(first + " == " + second + " : " + first == second);
13 System.out.println(first + " equals " + second + " : " + first.equals(second));
14 System.out.println("");
15 }
16 }
17
18
19 public class TestStringCompare
20 {
21 public static void main(String[] args)
22 {
23 String first = new String("Good");
24 String second = new String("Bad");
25 String third = first;
26
27 StringCompare.go(first, second);
28 StringCompare.go(third, second);
29 StringCompare.go(first, third);
30 }
31 }
3.14
时间： 2024-10-05 03:00:24