JAVA编程思想第四版—第二章—习题与答案

（1） 参照本章的第一个例子，创建一个“Hello，World”程序，在屏幕上简单地显示这句话。注意在自己的类里只需一个方法（“main”方法会在程序启动时执行）。记住要把它设为static形式，并置入自变量列表——即使根本不会用到这个列表。用javac编译这个程序，再用java运行它。 

 

public class HelloWorld{public static void main(String[] args){System.out.println("Hello,World");}}

(2) 写一个程序，打印出从命令行获取的三个自变量。

public class GetArgs{public static void main(String[] args){System.out.println(args[0]);System.out.println(args[1]);System.out.println(args[2]);}}//java GetArgs a 3 12

(3)

class Tree{int height;Tree(){System.out.println("Planting a seedling");height=0;}Tree(int initialHeight){height =initialHeight;System.out.println("Creating new tree that is "+height+" feet tall");}void info(){System.out.println("Tree is "+height+" feet tall");}void info(String s){System.out.println(s+":Tree is "+height+" feettall");}}public class OverLoading{public static void main(String[] args){new Tree();for (int i=0;i<5;i++){Tree t=new Tree(i);t.info();t.info("overloading method"); }}}

 

输出结果：

Microsoft Windows [版本 6.1.7600]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

D:\>javac OverLoading.java

D:\>java OverLoading
Planting a seedling
Creating new tree that is 0 feet tall
Tree is 0 feet tall
overloading method:Tree is 0 feettall
Creating new tree that is 1 feet tall
Tree is 1 feet tall
overloading method:Tree is 1 feettall
Creating new tree that is 2 feet tall
Tree is 2 feet tall
overloading method:Tree is 2 feettall
Creating new tree that is 3 feet tall
Tree is 3 feet tall
overloading method:Tree is 3 feettall
Creating new tree that is 4 feet tall
Tree is 4 feet tall
overloading method:Tree is 4 feettall

D:\>

 

（4）

//输出当前文件两倍长度public class Demo {public static void main(String[] args) {class StoreStuff {int storage(String s) {return s.length() * 2;}}StoreStuff x = new StoreStuff();System.out.println(x.storage("hi"));}}/**output:4/

 

（5）

public class DataOnlyTestTwo{public static void main(String[] args){class DataOnly{int a;double b;boolean c;void show(){System.out.println(a);System.out.println(b);System.out.println(c);}}DataOnly test=new DataOnly();test.a=234;test.b=2.1234545;test.c=true;test.show();}}/**output:2342.1234545true/

（6）

//精度设置，封装调用public class DataOnlyTest{public static void main(String[] args){class DataOnly{int a;double b;boolean c;void show(){System.out.println(a);System.out.println(b);System.out.println(c);}}DataOnly test=new DataOnly();test.a=20;test.b=3.141592653;test.c=true;test.show();}}/**output:203.141592653true*/

（7）

public class ATNTest{public static void main(String[] args){class ATypeName{    int i;double d;boolean b;void show(){System.out.println(i);System.out.println(d);System.out.println(b);}}ATypeName a=new ATypeName();a.i=3;a.d=2.71828;a.b=false;a.show();}}/**output:32.71828false*/

（8）

//数据元素测试public class Primitive{static int i;static char c;public static void main(String[] args){System.out.println("int="+i);System.out.println("char="+c);}}/**output:int = 0char =*/

 （9）

 

// object/Rainbow.java// TIJ4 Chapter Object, Exercise 11, page 90// Turn the AllColorsOfTheRainbow into a program that compiles and runs.public class RainBow {public static void main(String[] args) {AllTheColorsOfTheRainbow atc = new AllTheColorsOfTheRainbow();System.out.println("atc.anIntegerRepresentingColors = " + atc.anIntegerRepresentingColors);atc.changeColor(7);atc.changeTheHueOfTheColor(77);System.out.println("After color change, atc.anIntegerRepresentingColors = " + atc.anIntegerRepresentingColors);System.out.println("atc.hue = " + atc.hue);}}class AllTheColorsOfTheRainbow {int anIntegerRepresentingColors = 0;int hue = 0;void changeTheHueOfTheColor(int newHue) {hue = newHue;}int changeColor(int newColor) {return anIntegerRepresentingColors = newColor;}}

 

Microsoft Windows [版本 6.1.7600]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。D:\>javac RainBow.java

D:\>java RainBow
atc.anIntegerRepresentingColors = 0
After color change, atc.anIntegerRepresentingColors = 7
atc.hue = 77

D:\>

 

 （10）

class StaticTest{static int i=47;}class Increamentable{static void increment(){StaticTest.i++;};}public class Test{public static void main(String[] args){System.out.println("StaticTest.i="+StaticTest.i);StaticTest st1=new StaticTest();StaticTest st2=new StaticTest();System.out.println("st1.i="+st1.i);System.out.println("st2.i="+st2.i);Increamentable.increment();System.out.println("After Incrementable increment() called:");System.out.println("st1.i="+st1.i);System.out.println("st2.i="+st2.i);st1.i=3;System.out.println("After st1.i=3,");System.out.println("st1.i="+st1.i);System.out.println("st1.i="+st1.i);System.out.println("Create another StaticTest,st3");StaticTest st3=new StaticTest();System.out.println("st3.i="+st3.i);}}

 

 

Microsoft Windows [版本 6.1.7600]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

D:\>javac Test.java

D:\>java Test
StaticTest.i=47
st1.i=47
st2.i=47
After Incrementable increment() called:
st1.i=48
st2.i=48
After st1.i=3,
st1.i=3
st1.i=3
Create another StaticTest,st3
st3.i=3

D:\>

 

(11)

public class test {    public static void main(String[] args){    boolean b=false;    char c='x';    byte t=8;    short s=16;    int i=32;    long l=64;    float f=0.32f;    double d=0.64;    Boolean B=b;    System.out.println("boolean b="+b);    System.out.println("Boolean B="+B);    Character C=c;    System.out.println("char c="+c);    System.out.println("CharacterC="+C);    Byte T=t;    System.out.println("byte t="+t);    System.out.println("Byte T="+T);    Short S=s;    System.out.println("short s="+s);    System.out.println("Short S"+S);    Integer I=i;    System.out.println("int i="+i);    System.out.println("Integer I="+i);    Float F=f;    System.out.println("float f="+f);    System.out.println("Float F="+F);    Double D=d;    System.out.println("double d="+d);    System.out.println("Double D="+D);        }}