Java 7 Features

Binary Literals

Strings in switch Statement

Try with Resources or ARM (Automatic Resource Management)

Multiple Exception Handling

underscore in literals

Type Inference for Generic Instance Creation using Diamond Syntax

Improved Compiler Warnings and Errors When Using Non-Reifiable Formal Parameters with Varargs Methods


Try-with-resources statement

this:

BufferedReader br = new BufferedReader(new FileReader(path));
try {
   return br.readLine();
} finally {
   br.close();
}
becomes:

try (BufferedReader br = new BufferedReader(new FileReader(path)) {
   return br.readLine();
}
You can declare more than one resource to close:

try (
   InputStream in = new FileInputStream(src);
   OutputStream out = new FileOutputStream(dest))
{
 // code
}
Underscores in numeric literals

int one_million = 1_000_000;
Strings in switch

String s = ...
switch(s) {
 case "quux":
    processQuux(s);
    // fall-through

  case "foo":
  case "bar":
    processFooOrBar(s);
    break;

  case "baz":
     processBaz(s);
    // fall-through

  default:
    processDefault(s);
    break;
}
Binary literals

int binary = 0b1001_1001;
Improved Type Inference for Generic Instance Creation

Map> anagrams = new HashMap>();
becomes:

Map> anagrams = new HashMap<>();
Multiple exception catching

this:

} catch (FirstException ex) {
     logger.error(ex);
     throw ex;
} catch (SecondException ex) {
     logger.error(ex);
     throw ex;
}
becomes:

} catch (FirstException | SecondException ex) {
     logger.error(ex);
    throw ex;
}
SafeVarargs

this:

@SuppressWarnings({"unchecked", "varargs"})
public static void printAll(List... lists){
    for(List list : lists){
        System.out.println(list);
    }
}
becomes:

@SafeVarargs
public static void printAll(List... lists){
    for(List list : lists){
        System.out.println(list);
    }
}



Decorate Components with the JLayer Class:

The JLayer class is a flexible and powerful decorator for Swing components. The JLayer class in Java SE 7 is similar in spirit to the JxLayer project project at java.net. The JLayer class was initially based on the JXLayer project, but its API evolved separately.
Strings in switch Statement:

In the JDK 7 , we can use a String object in the expression of a switch statement. The Java compiler generates generally more efficient bytecode from switch statements that use String objects than from chained if-then-else statements.
Type Inference for Generic Instance:

We 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. Java SE 7 supports limited type inference for generic instance creation; you can only use type inference if the parameterized type of the constructor is obvious from the context. For example, the following example does not compile:

List l = new ArrayList<>();
l.add("A");
l.addAll(new ArrayList<>());
In comparison, the following example compiles:
List list2 = new ArrayList<>();
l.addAll(list2);
Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking:

In Java SE 7 and later, a single catch block can handle more than one type of exception. This feature can reduce code duplication. Consider the following code, which contains duplicate code in each of the catch blocks:

catch (IOException e) {
    logger.log(e);
    throw e;
}
catch (SQLException e) {
    logger.log(e);
    throw e;
}
In releases prior to Java SE 7, it is difficult to create a common method to eliminate the duplicated code because the variable e has different types. The following example, which is valid in Java SE 7 and later, eliminates the duplicated code:

catch (IOException|SQLException e) {
    logger.log(e);
    throw e;
}
The catch clause specifies the types of exceptions that the block can handle, and each exception type is separated with a vertical bar (|).
The java.nio.file package

The java.nio.file package and its related package, java.nio.file.attribute, provide comprehensive support for file I/O and for accessing the file system. A zip file system provider is also available in JDK 7