Some New features in JDK5 compare JDK1.4

 

 

1.   Enhanced 'for' loop .   -Java 5 added a new style of “for” loop (sometimes called "for-in" loops)   5.0 1.4 for (type variable : array){   // body }   for (int i = 0; i < array.length; i++){    type variable = array[i];    //body } for (type variable:arrayList){    //body } for (int i=0;i<arrayList.size();i++){    type variable =(type)arrayList.get(i);    //body } – This code loops through each entry in an array or collection object returning one value at a time  for processing -- an Iterator is used without an Iterator being defined! 2. Generics We use ‘ArrayList’ ,as example . 5.0 1.4 ArrayList<Employee> arrayList =       new ArrayList<Employee>() ArrayList arrayList =new ArrayList(); Employee e=arrayList.get(i) Employee e=(Employee) arrayList.get(i)       Now with this new feature you don't need so much force convert. 3. Enum     Another new Java 5 feature that looks familiar to C programmers is the "Enum" data type. Enum allows assignment of a specific set of values  to associated .You can see many in JDK source 1.5.        public class UsingEnum {           public enum Weekdays {              Thursday, Friday,  Monday, Tuesday, Wednesday,              Saturday, Sunday};           }         } 4. AutoBoxing Java 5 (Java 1.5) and later automatically “box”and ”unbox” values.  – The advent of automatic Boxing and automatic Unboxing greatly simplifies code when using   Collection and other types of objects  – Boxing and Unboxing is also important since Primitive data and Reference Type data are stored in different places; primitives representing local variables are stored on the stack while objects are stored in heap memory.     Example: 5.0 1.4 Integer wrapper = n; Integer wrapper = new Integer(n);   5.0 1.4 int n = wrapper; int n = wrapper.intValue();   5. Variable Argument Lists                                                     New variable argument lists (VarArgs) allow specification of a method that can accept a final parameter of the same type with the number of values to be determined at runtime. Below are some rules related to this. - Only one variable argument list is allowed per method – Variable list must be the last argument defined for the method – The ellipsis "…" is used to indicate that an argument might appear a variable number of times Example:   5.0 1.4 method(other params, p1, p2, p3) method(other params, new Type[] { p1, p2, p3 }) public Auto (String year, String make, String model, String... options) { … ) ............ Auto myTruck = new Auto("1997","Ford","Four-wheel drive","power windows", "air-conditioning"); 6. Changeable return value   Before JDK5.0，you can’t change the return value.Now with this new feature You can do it here is an example. 5.0 1.4 public Employee clone() { ... } ... Employee cloned = e.clone();   public Object clone() { ... } ... Employee cloned = (Employee) e.clone();     7. Static Imports                                           Java 5 (Java 1.5) allows import of static items when methods or variables are used repeatedl but JDK 1.4 doesn’t support。 5.0 1.4 import static java.lang.Math; import static java.lang.System; ... out.println(sqrt(PI)); System.out.println(Math.sqrt(Math.PI));     8.Metadata Annotations   Java 5 introduced a method for adding metadata to package and type declarations, methods,  constructors, parameters, fields, and variables. Some of them are - @Override - @Deprecated - @SupressWarnings 9. Scanner Input                                                JDK 5.0 does’t have Scanner class，you need use JOptionPane.showInputDialog class。 5.0 1.4 Scanner in = new Scanner(System.in); System.out.print(prompt); int n = in.nextInt(); double x = in.nextDouble(); String s = in.nextLine(); String input = JOptionPane.showInputDialog(prompt); int n = Integer.parseInt(input); double x = Double.parseDouble(input); s = input;

10. StringBuilder.class The new class, java.lang.StringBuilder provides a faster alternative to StringBuffer – In most ways StringBuilder works exactly the same as StringBuffer – StringBuilder is faster than StringBuffer because it is not ThreadSafe (multiple threads should not access StringBuilder objects without Synchronizing) – Use StringBuilder when speed is important in a single-thread environment and use StringBuffer if multiple threads might require access.