Java-Java编程思想第四版 第十三章 练习

练习2：// Repair InfiniteRecursion.javaimport java.util.*;public class Ja13_3_2 {public String toString() {return " InfiniteRecursion address: " + super.toString() + "\n";}public static void main(String[] args) {List<Ja13_3_2> v =new ArrayList<Ja13_3_2>();for(int i = 0; i < 10; i++)v.add(new Ja13_3_2());System.out.println(v);}}

练习3：// Modify Turtle.java so that it sends all output to System.err.import java.io.*;import java.util.*;public class Ja13_5_3{private String name;private Formatter f;public Ja13_5_3(String name, Formatter f) {this.name = name;this.f = f;}public void move(int x, int y) {f.format("%s The Ja13_5_3 is at (%d,%d)\n", name, x, y);}public static void main(String[] args) {PrintStream outAlias = System.err;Ja13_5_3 tommy = new Ja13_5_3("Tommy",new Formatter(System.out));Ja13_5_3 terry = new Ja13_5_3("Terry",new Formatter(outAlias));tommy.move(0,0);terry.move(4,8);tommy.move(3,4);terry.move(2,5);tommy.move(3,3);terry.move(3,3);}}

练习4：/* Modify Ja13_5_4.java so that the widths are all controlled by a single* set of constant values. The goal is to allow you to easily change a width* by changing a single value in one place.*/import java.util.*;public class Ja13_5_4 {private double total = 0;private Formatter f = new Formatter(System.out);private int i=20;private String s1="%-"+i+"s %5s %10s\n";private String s2="%-"+i+".15s %5d %10.2f\n";private String s3="%-"+i+"s %5s %10.2f\n";public void printTitle() {f.format(s1, "Item", "Qty", "Price");f.format(s1, "----", "---", "-----");}public void print(String name, int qty, double price) {f.format(s2, name, qty, price);total += price;}public void printTotal() {f.format(s3, "Tax", "", total*0.06);f.format("%-15s %5s %10s\n", "", "", "-----");f.format(s3, "Total", "",total * 1.06);}public static void main(String[] args) {Ja13_5_4 receipt = new Ja13_5_4();receipt.printTitle();receipt.print("Jack's Magic Beans", 4, 4.25);receipt.print("Princess Peas", 3, 5.1);receipt.print("Three Bears Porridge", 1, 14.29);receipt.printTotal();}}

练习5：/* For each of the basic conversion types in the above table, write the* most complex formatting expression possible. That is, use all the possible* format specifiers available for that conversion type.*/import java.math.*;import java.util.*;class Conversion{}public class Ja13_5_5 {public static void main(String[] args) {Formatter f = new Formatter(System.out);char u = 'a';System.out.println("char u = \'a\'");f.format("%-2s%-2S%-2c%-2C%-5b%-5B%-3h%-3H%%\n", u,u,u,u,u,u,u,u);int v = 121;System.out.println("int v = 121");f.format("%-4s%-4S%-4d%-4c%-4C%-5b%-5B%-4x%-4X%-4h%-4H%%\n", v,v,v,v,v,v,v,v,v,v,v);BigInteger w = new BigInteger("50000000000000");System.out.println("BigInteger w = 50000000000000");f.format("%-15s%-15S%-5b%-5B%-15x%-15X%-5h%-5H%%\n", w,w,w,w,w,w,w,w);double x = 179.543;System.out.println("double x = 179.543");f.format("%-8s%-8S%-5b%-5B%-15f%-15e%-15E%-12h%-12H%%\n", x,x,x,x,x,x,x,x,x);Conversion y = new Conversion();System.out.println("Conversion y = new Conversion()");f.format("%-20s%-20S%-5b%-5B%-10h%-10H%%\n", y,y,y,y,y,y);boolean z = false;System.out.println("boolean z = false");f.format("%-7s%-7S%-7b%-7B%-7h%-7H%%\n", z,z,z,z,z,z);}}/*char u = 'a'a A a A true TRUE 61 61 %int v = 121121 121 121 y Y true TRUE 79 79 79 79 %BigInteger w = 5000000000000050000000000000 50000000000000 true TRUE 2d79883d2000 2D79883D2000 8842a1a78842A1A7%double x = 179.543179.543 179.543 true TRUE 179.543000 1.795430e+02 1.795430E+02 1ef462c1EF462C %Conversion y = new Conversion()Conversion@75ad44f6 CONVERSION@75AD44F6 true TRUE 75ad44f6 75AD44F6 %boolean z = falsefalse FALSE false FALSE 4d5 4D5 %*/

练习6：/* Create a class that contains int, long, float, and double fields. Create* a toString() method for this class that uses String.format(), and demonstrate* that your class works correctly.*/import java.util.*;import static net.mindview.util.Print.*;class A{private int i;private float f;private long l;private double d;A(int i,float f,long l,double d){this.i=i;this.f=f;this.l=l;this.d=d;}public String toString(){return String.format("%5d,%5.5f,%5d,%5.10g",i,f,l,d);}}public class Ja13_5_6{public static void main(String[] args){A a=new A(5,5.55f,10000l,8.666666e01);System.out.println(a);}}//g表示double，long也用d表示

练习7：/* Using the documentation for java.util.regex.Pattern as a resource,* write and test a regular expression that checks a sentence to see* that it begins with a captial letter and ends with a period.*/import static net.mindview.util.Print.*;public class Ja13_6_7{public static void main(String[] agrs){String s="Using the documentation for java.util.regex.Pattern.";print(s.matches("^[A-Z].*\\."));}}

练习8：// Split the string Splitting.knights on the words "the" or "you."import static net.mindview.util.Print.*;import java.util.*;public class Ja13_6_8{public static void main(String[] agrs){String s="Then, when you have found the shrubbery, you must " +"cut down the mightiest tree in the forest... " +"with... a herring!";print(Arrays.toString(s.split("the|you")));}}

练习9：// Using the documentation for java.util.regex.Pattern as a resource,// replace all the vowels in Splitting.knights with underscores.import static net.mindview.util.Print.*;import java.util.*;public class Ja13_6_9{public static void main(String[] agrs){String s="Then, when you have found the shrubbery, you must " +"cut down the mightiest tree in the forest... " +"with... a herring!";print(s.replaceAll("a|o|e|i|u","_"));}}

练习10：/* For the phrase "Java now has regular expressions" evaluate whether the following* expressions will find a match:* ^Java* \Berg.** n.w\s+h(a|i)s* S?* S+* s{4}* s{1}.* s{0,3}*/import java.util.regex.*;import static net.mindview.util.Print.*;public class Ja13_6_10{public static void main(String[] args){String s[]={"^Java","\\Berg.*","n.w\\s+h(a|i)s","S?","S+","s{4}","s{1}.","s{0,3}"};String ss="Java now has regular expressions";for(String regex:s){Pattern p=Pattern.compile(regex);Matcher m=p.matcher(ss);while(m.find())print(regex+": "+m.group());}}}

练习11：/* Apply the regular expression:* (?i)((^[aeiou])|(\s+[aeiou]))\W+?[aeiou]\b* to* "Arline ate eight apples and one orange while Anita hadn't any"*/import java.util.regex.*;import static net.mindview.util.Print.*;public class Ja13_6_11{public static void main(String[] args){Pattern p=Pattern.compile("(?i)((^[aeiou])|(\\s+[aeiou]))\\W+?[aeiou]\\b");Matcher m=p.matcher("Arline ate eight apples and one orange while Anita hadn't any");if(m.find())print(m.group());else print("no");}}

练习12：/* Modify Groups.java to count all of the unique words that do not start with a* capital letter.*/import java.util.*;import java.util.regex.*;import static net.mindview.util.Print.*;public class Ja13_6_12{static public final String POEM ="Twas brillig, and the slithy toves\n" +"Did gyre and gimble in the wabe.\n" +"All mimsy were the borogoves,\n" +"And the mome raths outgrabe.\n\n" +"Beware the Jabberwock, my son,\n" +"The jaws that bite, the claws that catch.\n" +"Beware the Jubjb56eub bird, and shun\n" +"The frumious Bandersnatch.";public static void main(String[] args){Matcher m=Pattern.compile("(?m)(^|\\s+)([a-z]\\w+)").matcher(POEM);//Matcher m=Pattern.compile("((^[a-z])|\\s+)([a-z]\\w+)").matcher(POEM);int i=0;Set<String> set=new LinkedHashSet<String>();while(m.find()){set.add(m.group().trim());}print(set.size());print(set);}}//(?m)((^|\\W+)([^A-Z]\\w+)\\W+)+ //前后空格会挤掉后一个单词//(?m)(^|\\W+)([^A-Z]\\w+) // \\W+会把逗号也牵扯进来//((^[a-z])|\\s+)([a-z]\\w+)//

练习13：// Modify StartEnd.java so that it uses Groups.POEM as input, but still produces positive// outputs for find(), lookingAt() and matches().import java.util.regex.*;import static net.mindview.util.Print.*;import static strings.Groups.*;public class Ja13_13{public static String input ="As long as there is injustice, whenever a\n" +"Targathian baby cries out, wherever a distress\n" +"signal sounds among the stars ... We'll be there.\n" +"This fine ship, and this fine crew ...\n" +"Never give up! Never surrender!";private static class Display {private boolean regexPrinted = false;private String regex;Display(String regex) { this.regex = regex; }void display(String message) {if(!regexPrinted) {print(regex);regexPrinted = true;}print(message);}}static void examine(String s, String regex) {Display d = new Display(regex);Pattern p = Pattern.compile(regex);Matcher m = p.matcher(s);while(m.find())d.display("find() '" + m.group() +"' start = "+ m.start() + " end = " + m.end());if(m.lookingAt()) // No reset() necessaryd.display("lookingAt() start = "+ m.start() + " end = " + m.end());if(m.matches()) // No reset() necessaryd.display("matches() start = "+ m.start() + " end = " + m.end());}public static void main(String[] args) {for(String in : POEM.split("\n")) {print("input : " + in);for(String regex : new String[]{"\\w*ere\\w*","\\w*ever", "T\\w+", "Did.*"})examine(in, regex);}}}

练习14：// Rewrite SplitDemo using String.split().import java.util.regex.*;import java.util.*;import static net.mindview.util.Print.*;public class Ja13_14{public static void main(String[] args){String input ="This!!unusual use!!of exclamation!!points";print(Arrays.toString(input.split("!!")));// Only do the first three:print(Arrays.toString(input.split("!!", 3)));}}

练习15：// Modify JGrep.java to accept flags as arguments (e.g., Pattern.CASE_INSENSITIVE,// Pattern.MULTILINE).// {Args: JGrep15.java "\b[Ssct]\w+", Pattern.CASE_INSENSITIVE}import java.util.regex.*;import net.mindview.util.*;public class Ja13_15{public static void main(String[] args){if(args.length < 2) {System.out.println("Usage: java JGrep file regex");System.exit(0);}Pattern p = Pattern.compile(args[1],Pattern.CASE_INSENSITIVE|Pattern.MULTILINE);// Iterate through the lines of the input file:int index = 0;Matcher m = p.matcher("");for(String line : new TextFile(args[0])) {m.reset(line);while(m.find())System.out.println(index++ + ": " +m.group() + ": " + m.start());}}}

练习16：/* Modify JGrep.java to accept a directory name or a file name as argument* (if a directory is provided, search should include all files in the* directory). Hint: You can generated a list of file names with:* File[] files = new File(".").listFiles();*/import java.util.regex.*;import net.mindview.util.*;import java.io.*;import static net.mindview.util.Print.*;public class Ja13_16{public static void main(String[] args){/*if(args.length < 2) {System.out.println("Usage: java JGrep file regex");System.exit(0);}*/Pattern p = Pattern.compile("IMPORT.*;",Pattern.CASE_INSENSITIVE|Pattern.MULTILINE);// Iterate through the lines of the input file:int index = 0;Matcher m = p.matcher("");File[] files = new File("C:\\Thinking_In_Java\\abc").listFiles();for(File file:files){for(String line : new TextFile(file.getName())) {m.reset(line);while(m.find())System.out.println(index++ + ": " +m.group() + ": " + m.start());}}}}练习17：/* Write a program that reads a Java source-code file (you provide the* file name on the command line) and displays all the comments.*/import java.util.regex.*;import net.mindview.util.*;import static net.mindview.util.Print.*;public class Ja13_17{public static void main(String[] args){String ar="Ja13_16.java";Matcher m=Pattern.compile("(/\\*(.*)\\*/)|(.*(//.*$))",Pattern.DOTALL|Pattern.MULTILINE).matcher("");for(String line:new TextFile(ar)){m.reset(line);while(m.find()){print(m.group(1)+"\n"+m.group(4));}}}}//无法获取多行/**/注释？？练习18：/* Write a program that reads a Java source-code file (you provide the* file name on the command line) and displays all the string literals* in the code.*/import java.util.regex.*;import net.mindview.util.*;import static net.mindview.util.Print.*;public class Ja13_18{public static void main(String[] args){String ar="Ja13_16.java";Matcher m=Pattern.compile("(\\w+)\\W+",Pattern.DOTALL|Pattern.MULTILINE).matcher("");for(String line:new TextFile(ar)){m.reset(line);while(m.find()){print(m.group(1));}}}}练习19：/* Building on the previous two exercises, write a program that examines* Java source-code and produces all the class names used in a particular* program.*/import java.util.regex.*;import net.mindview.util.*;import static net.mindview.util.Print.*;public class Ja13_19{public static void main(String[] args){String ar="Ja13_16.java";Matcher m=Pattern.compile("class (\\w+)\\W+",Pattern.DOTALL|Pattern.MULTILINE).matcher("");for(String line:new TextFile(ar)){m.reset(line);while(m.find()){print(m.group(1));}}}}练习20：/* Create a class that contains int, long, float and double and String fields.* Create a constructor for this class that takes a single String argument, and* scans that string into the various fields. Add a toString(0 method and* demonstrate that your class works correctly.*/import java.util.*;import static net.mindview.util.Print.*;import java.io.*;public class Ja13_20{public static void main(String[] args){String s="5 57673 4.5787 9.3557 dasfdsv";Scanner sc=new Scanner(new BufferedReader(new StringReader(s)));int i=sc.nextInt();long l=sc.nextLong();float f=sc.nextFloat();double d=sc.nextDouble();String ss=sc.next();print(" i "+i+" l: "+l+" f: "+f+" "+" d: "+d+" ss: "+ss);}}