Sunday, April 2, 2017

Java 7 Features

  • Binary Literals  - In Java SE 7, the integral types (byte, short, int, and long) can also be expressed using the binary number system. To specify a binary literal, add the prefix 0b or 0B to the number.
Before:
public void testBinaryIntegralLiterals(){
        int binary = 8;
        if (binary == 8){
            System.out.println(true);
        } else{
            System.out.println(false);
        }
}
Java7:
public void testBinaryIntegralLiterals(){
        int binary = 0b1000; //2^3 = 8
        if (binary == 8){
            System.out.println(true);
        } else{
            System.out.println(false);
        }
}

  • Underscores in Numeric Literals - Any number of underscore characters (_) can appear anywhere between digits in a numerical literal. This feature enables you, for example, to separate groups of digits in numeric literals, which can improve the readability of your code.
public void testUnderscoresNumericLiterals() {
    int oneMillion_ = 1_000_000; //new
    int oneMillion = 1000000;
    if (oneMillion_ == oneMillion){
        System.out.println(true);
    } else{
        System.out.println(false);
    }
}

Before:
public void testStringInSwitch(String param){
       final String JAVA5 = "Java 5";
       final String JAVA6 = "Java 6";
       final String JAVA7 = "Java 7";
       if (param.equals(JAVA5)){
           System.out.println(JAVA5);
       } else if (param.equals(JAVA6)){
           System.out.println(JAVA6);
       } else if (param.equals(JAVA7)){
           System.out.println(JAVA7);
       }
   }
Java7:
public void testStringInSwitch(String param){
       final String JAVA5 = "Java 5";
       final String JAVA6 = "Java 6";
       final String JAVA7 = "Java 7";
       switch (param) {
           case JAVA5:
               System.out.println(JAVA5);
               break;
           case JAVA6:
               System.out.println(JAVA6);
               break;
           case JAVA7:
               System.out.println(JAVA7);
               break;
       }
   }

  • Type Inference for Generic Instance Creation (Diamond Operator) - You can replace the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (<>) as long as the compiler can infer the type arguments from the context. This pair of angle brackets is informally called the diamond.
Before:
public void testDinamond(){
    List list = new ArrayList();
    Map> map = new HashMap>();
}
Java7:
public void testDinamond(){
    List list = new ArrayList<>();
    Map> map = new HashMap<>();
}

  • The try-with-resources Statement - The try-with-resources statement is a try statement that declares one or more resources. A resource is an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Any object that implements the new java.lang.AutoCloseable interface or the java.io.Closeable interface can be used as a resource. The classes java.io.InputStream, OutputStream, Reader, Writer, java.sql.Connection, Statement, and ResultSet have been retrofitted to implement the AutoCloseable interface and can all be used as resources in a try-with-resources statement.

Before:
public void testTryWithResourcesStatement() throws FileNotFoundException, IOException{
     FileInputStream in = null;
    try {
        in = new FileInputStream("java7.txt");
        System.out.println(in.read());
    } finally {
        if (in != null) {
            in.close();
        }
    }
}
Java 7:
public void testTryWithResourcesStatement() throws FileNotFoundException, IOException{
    try (FileInputStream in = new FileInputStream("java7.txt")) {
        System.out.println(in.read());
    }
}

Before:
public void testMultiCatch(){
     try {
         throw new FileNotFoundException("FileNotFoundException");
     } catch (FileNotFoundException fnfo) {
         fnfo.printStackTrace();
     } catch (IOException ioe) {
         ioe.printStackTrace();
}
Java 7:
public void testMultiCatch(){
    try {
        throw new FileNotFoundException("FileNotFoundException");
    } catch (FileNotFoundException | IOException fnfo) {
        fnfo.printStackTrace();
    }
}

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