Java 10 Features

1. 🔹 Local Variable Type Inference (var)

Description: Allows you to declare local variables using var, letting the compiler infer the type.

Example:

var name = "Java";          // inferred as String
var count = 10;             // inferred as int
var list = List.of("A", "B", "C"); // inferred as List<String>

🔸 Only for local variables (not class members, parameters, or return types).

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2. 🔹 Unmodifiable Collectors

Improvement in Collectors.toUnmodifiableList(), Set, and Map.

Example:

var list = List.of("A", "B", "C");
var unmodifiableList = list.stream()
                           .collect(Collectors.toUnmodifiableList());

Trying to modify the list will throw UnsupportedOperationException.

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3. 🔹 Optional.orElseThrow() Without Arguments

Description: Simplified way to throw NoSuchElementException if value is not present.

Example:

Optional<String> name = Optional.of("Java");
System.out.println(name.orElseThrow()); // no args needed

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4. 🔹 Application Class-Data Sharing (AppCDS)

Benefit: Reduces JVM startup time and memory footprint by sharing common class metadata across JVMs.

Use Case: Large-scale Java applications and microservices.

🛠 Requires specific setup with -Xshare:on.

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5. 🔹 G1 Garbage Collector Improvements

Description: G1 GC now supports full parallel compaction — improving pause times.

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6. 🔹 Root Certificates Included

Java 10 comes with a default set of root SSL certificates, improving out-of-the-box security for HTTPS connections.

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7. 🔹 Thread-Local Handshakes

A new JVM mechanism to allow fine-grained pausing of threads for diagnostics and memory management.

🔍 More efficient than global safepoints.

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8. 🔹 Heap Allocation on Alternative Memory Devices

Supports systems with multi-tiered memory (e.g., DRAM + NVDIMM), allowing Java to allocate heap memory selectively.

Useful for large-scale enterprise deployments.

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9. 🔹 Experimental Java-Based JIT Compiler (Graal)

You can use Graal as an experimental JIT compiler with the JVM:

java -XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler ...

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🔚 Summary Table

Feature	Benefit
var for local variables	Cleaner syntax, type inference
Unmodifiable collectors	Immutable collections
Optional.orElseThrow()	Simplified null-checks
AppCDS	Faster startup, reduced memory
G1 GC enhancements	Shorter pause times
Root certificates	Secure HTTPS out-of-the-box
Thread-local handshakes	Better diagnostics, perf
Heap on alternative memory	Efficient memory usage
Graal JIT compiler	Performance tuning