Generic Classes and Methods - Java: How to Program Early Objects - page 860

RawTypeTest.java:17: warning: [unchecked] unchecked conversion
found : Stack
required: Stack<java.lang.Integer>
Stack<Integer> integerStack = new Stack(10);
^
RawTypeTest.java:19: warning: [unchecked] unchecked conversion
found : Stack
required: Stack<java.lang.Double>
testPush("rawTypeStack1", rawTypeStack1, doubleElements);
^
RawTypeTest.java:19: warning: [unchecked] unchecked method invocation:
<T>testPush(java.lang.String,Stack<T>,T[]) in RawTypeTest is applied to
(java.lang.String,Stack,java.lang.Double[])
testPush("rawTypeStack1", rawTypeStack1, doubleElements);
^
RawTypeTest.java:20: warning: [unchecked] unchecked conversion
found : Stack
required: Stack<T>
testPop("rawTypeStack1", rawTypeStack1);
^
RawTypeTest.java:20: warning: [unchecked] unchecked method invocation:
<T>testPop(java.lang.String,Stack<T>) in RawTypeTest is applied to
(java.lang.String,Stack)
testPop("rawTypeStack1", rawTypeStack1);
^
RawTypeTest.java:21: warning: [unchecked] unchecked conversion
found : Stack
required: Stack<java.lang.Double>
testPush("rawTypeStack2", rawTypeStack2, doubleElements);
^
RawTypeTest.java:21: warning: [unchecked] unchecked method invocation:
<T>testPush(java.lang.String,Stack<T>,T[]) in RawTypeTest is applied to
(java.lang.String,Stack,java.lang.Double[])
testPush("rawTypeStack2", rawTypeStack2, doubleElements);
^
RawTypeTest.java:22: warning: [unchecked] unchecked conversion
found : Stack
required: Stack<T>
testPop("rawTypeStack2", rawTypeStack2);
^
RawTypeTest.java:22: warning: [unchecked] unchecked method invocation:
<T>testPop(java.lang.String,Stack<T>) in RawTypeTest is applied to
(java.lang.String,Stack)
testPop("rawTypeStack2", rawTypeStack2);
^
9 warnings
Fig. 20.12 | Warning messages from the compiler.
20.8 Wildcards in Methods That Accept Type
Parameters
In this section, we introduce a powerful generics concept known as wildcards . Let's con-
sider an example that motivates wildcards. Suppose that you'd like to implement a generic
method sum that totals the numbers in a collection, such as an ArrayList . You'd begin by