// Put elements to the map.
tm.put("John Doe", new Double(3434.34));
tm.put("Tom Smith", new Double(123.22));
tm.put("Jane Baker", new Double(1378.00));
tm.put("Tod Hall", new Double(99.22));
tm.put("Ralph Smith", new Double(-19.08));
// Get a set of the entries.
Set<Map.Entry<String, Double>> set = tm.entrySet();
// Display the elements.
for(Map.Entry<String, Double> me : set) {
System.out.print(me.getKey() + ": ");
System.out.println(me.getValue());
}
System.out.println();
// Deposit 1000 into John Doe's account.
double balance = tm.get("John Doe");
tm.put("John Doe", balance + 1000);
System.out.println("John Doe's new balance: " +
tm.get("John Doe"));
}
}
Here is the output; notice that the accounts are now sorted by last name:
Jane Baker: 1378.0
John Doe: 3434.34
Todd Hall: 99.22
Ralph Smith: -19.08
Tom Smith: 123.22
John Doe's new balance: 4434.34
The comparator class TComp compares two strings that hold first and last names. It does
so by first comparing last names. To do this, it finds the index of the last space in each string
and then compares the substrings of each element that begin at that point. In cases where last
names are equivalent, the first names are then compared. This yields a tree map that is sorted
by last name, and within last name by first name. You can see this because Ralph Smith comes
before Tom Smith in the output.
The Collection Algorithms
The Collections Framework defines several algorithms that can be applied to collections and
maps. These algorithms are defined as static methods within the Collections class. They are
summarized in Table 17-14. As explained earlier, beginning with JDK 5 all of the algorithms
have been retrofitted for generics. Although the generic syntax might seem a bit intimidating
at first, the algorithms are as simple to use as they were before generics. It's just that now,
they are type safe.
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