| << Chapter < Page | Chapter >> Page > |
| Figure 2 - Question 6. |
|---|
abcd efgh_ijklm
abcd 500_ijklm500 abcd_ijklm |
Design and write a class named A07Foo which, when combined with the class defined in Listing 3 will compile, run, and produce the output shown in Figure 3 .
| Listing 3 - Question 7. |
|---|
/*File Q07.java
************************************************/public class Q07{public static void main(String[] args){A07Foo<Integer,String>fooA =
new A07Foo<>(" ijkl");
fooA.set(new Integer(-300));System.out.println(
fooA.cat("abcd "," efgh "));System.out.println(
fooA.cat("abcd ",new Integer(500)));System.out.println(
fooA.cat(new Integer(500)," abcd "));}//end main
}//end class Q07//=============================================// |
| Figure 3 - Question 7. |
|---|
abcd efgh -300 ijkl
abcd 500-300 ijkl500 abcd -300 ijkl |
True or False: The syntax for a generic method includes a type parameter, inside angle brackets, and appears after the method's return type
What is the meaning of the following two images?
These images were inserted here simply to insert some space between the questions and the answers to keep them from being visible on the screen at thesame time.
This image was also inserted for the purpose of inserting space between the questions and the answers.
False. The statement should read:
"The syntax for a generic method includes a type parameter, inside angle brackets, and appears before the method's return type"
One possible solution is provided in Listing 4 below.
| Listing 4 - Answer 7. |
|---|
/*File A07Foo.java
************************************************///A generic class
public class A07Foo<T3,T4>{
private T3 tC;private T4 tD;//constructor
public A07Foo(T4 tD){this.tD = tD;
}//end constructor//A set methodpublic void set(T3 tC){
this.tC = tC;}//end cat//A generic concatenation method
public<T1,T2>String cat(T1 tA,T2 tB){
return tA.toString() + tB.toString()+ tC.toString() + tD.toString();
}//end cat}//end A07Foo//=============================================// |
One possible solution is provided in Listing 5 below.
| Listing 5 - Answer 6. |
|---|
/*File A06Foo.java
************************************************/public class A06Foo<T3>{
private T3 tC;//A set methodpublic void set(T3 tC){
this.tC = tC;}//end cat//A generic concatenation method
public<T1,T2>String cat(T1 tA,T2 tB){
return tA.toString() + tB.toString()+ tC.toString();
}//end cat}//end A06Foo//=============================================// |
One possible solution is provided in Listing 6 below.
| Listing 6 - Answer 5. |
|---|
/*File A05Foo.java
************************************************/public class A05Foo{
//A generic concatenation methodpublic<T1,T2>String cat(T1 tA,T2 tB){
return tA.toString() + tB.toString();}//end cat
}//end A05Foo//=============================================// |
False. Generic class constructors are allowed.
True.
False. The statement should read as follows:
"Defining a generic method is similar to declaring a generic type, but the type parameter's scope is limited to the method where it is declared."
True.
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