Java 7 Features

Small improvements to a school day can matter more than big ones: a door that closes by itself, a register that fills in the date automatically, a corridor sign that is finally easy to read. Java 7, released in July 2011 after a five-year wait, was a release of exactly those small, practical fixes. Its features (collected under the name "Project Coin") removed boilerplate that Java programmers had been typing for years. In this lesson, you will get a quick reference to what Java 7 added, see the before and after in code, and find the lesson that covers each feature.

What Did Java 7 Add?

Java 7 is the Java release that added try-with-resources, multi-catch, the diamond operator, strings in switch, binary literals and underscores in numbers to the language, and NIO.2 (Path, Files), the fork/join framework and the Objects utility class to the library. It was the first release under Oracle, which had bought Sun Microsystems in 2010.

Language Features

Library and JVM Features

Before and After Java 7

Let's see a program that uses most of the Java 7 additions together.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
 
public class Coin {
    static String dayType(String day) {
        switch (day) {                                   // strings in switch
            case "SAT":
            case "SUN":
                return "holiday";
            default:
                return "school day";
        }
    }
 
    public static void main(String[] args) throws IOException {
        List<String> names = new ArrayList<>();          // diamond
        names.add("Navika");
        names.add("Advitha");
 
        int fee = 1_50_000;                              // underscores
        int flags = 0b0101;                              // binary literal
        System.out.println("fee " + fee + ", flags " + flags);
        System.out.println("MON is a " + dayType("MON"));
 
        Path file = Files.createTempFile("roll", ".txt"); // NIO.2
        Files.write(file, names);
        try (var lines = Files.lines(file)) {            // try-with-resources
            lines.forEach(n -> System.out.println("read " + n));
        }
        Files.delete(file);
 
        try {
            Object o = names.get(5);
        } catch (IndexOutOfBoundsException | NullPointerException e) {
            System.out.println("multi-catch caught "    // multi-catch
                    + e.getClass().getSimpleName());
        }
        System.out.println(Objects.equals(null, null));  // Objects helper
    }
}

fee 150000, flags 5
MON is a school day
read Navika
read Advitha
multi-catch caught IndexOutOfBoundsException
true

Explanation:

1. new ArrayList<>() saves repeating <String>.
2. 1_50_000 groups digits the Indian way (one lakh fifty thousand); the underscores are ignored by the compiler. 0b0101 is 5.
3. Files.write and Files.lines read and write a whole file in one call. The try (...) block closes the stream automatically. (var and the lambda come from later releases; in Java 7 you would write the full type and a loop.)
4. Multi-catch handles two exception types in one catch block.
5. Objects.equals(null, null) returns true instead of throwing a NullPointerException.

Practice

1. Easy: Rewrite this with Java 7 features: Map<String, List<Integer>> marks = new HashMap<String, List<Integer>>(); int crore = 10000000;
2. Harder: Write a method that copies a text file with Files.copy, catches NoSuchFileException | AccessDeniedException in one block, and uses try-with-resources to read the copied file's first line with a BufferedReader.

Key Takeaways