Solutions to Self-Study Exercises

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Solution 7.1	silly silly silly stuff
Solution 7.2	String str1 = ""; String str2 = new String("stop"); String str3 = str1 + str2;
Solution 7.3	15 "551" "5175"
Solution 7.4	See Figure 7.25. Figure 7.25. Answer to Exercise 7.4. Note that s1 is null because it has not been instantiated and has not been assigned a literal value.

Solution 7.5	"45" "121" "X"
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Solution 7.6	String.valueOf(100) String.valueOf('V'); String s = new String(String.valueOf(X * Y));

Solution 7.7	0 1 -1
Solution 7.8	16 "16" 1 15 1 13 7 3 7 7 3
Solution 7.9	Evaluate the following expression: String tricky = "abcdefg01234567"; tricky.indexOf(String.valueOf(tricky.indexOf("c"))); tricky.indexOf(String.valueOf(2)); tricky.indexOf("2"); Answer: 9

Solution 7.10	"uvwxyz" "bcde" "xyz" "xy" "xyz"
Solution 7.11	"uvwxyz" "bcde" "xyz" "xyz" "xyz"

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Solution 7.12	A class to test the string methods. public class StringProcessorTest { public static void main(String[] args) { KeyboardReader kb = new KeyboardReader(); kb.prompt("Input a String or - stop - to quit: "); String str = kb.getKeyboardInput(); while (!str.equals("stop")){ kb.display("Testing printLetters()\n"); StringProcessor.printLetters(str); kb.display("testing countChars()\n"); kb.display("Total occurences of e = "); kb.display(StringProcessor.countChar(str,'e') + "\n"); kb.display("Testing reverse()\n"); kb.display(StringProcessor.reverse(str)+ "\n"); kb.display("Testing capitalize()\n"); kb.display(StringProcessor.capitalize(str) + "\n\n"); kb.prompt("Input a String or stop to quit: "); str = kb.getKeyboardInput(); } // while } // main() } // StringProcessorTest class
Solution 7.13	Method to remove all blanks from a string: // Pre: s is a non null string // Post: s is returned with all its blanks removed public String removeBlanks(String s) { StringBuffer result = new StringBuffer(); for (int k = 0; k < s.length(); k++) if (s.charAt(k) != ' ') // If this is not a blank result.append(s.charAt(k)); // append it to result return result.toString(); }

Solution 7.14	A Alpha Z Zero Zeroes a alpha bath bin z zero
Solution 7.15	To modify precedes so that it also returns true when its two string arguments are equal, just change the operator in the final return statement to <=: if (s1.charAt(k) <= s2.charAt(k) ) return true;

Solution 7.16	true true false false false true false false false
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Solution 7.17	The variables in TestStringEquals are declared static because they are used in static methods. Whenever you call a method directly from main(), it must be static because main() is static. Remember that static elements are associated with the class, not with its instances. So main() can only use static elements because they don't depend on the existence of instances.
Solution 7.18	String s3 = s1.substring(s1.indexOf('n')) + s1.substring(0,s1.indexOf('n')); String s4 = s2.substring(6) + " " + s2.substring(0,5); String s5 = s2.substring(0,6) + s1.substring(0,3);