Java on Haoxiqiang's Blog

Java Reflection: Modifying Private Static Final Fields

Tue, 16 Jun 2015 11:09:06 +0000

While debugging memory leaks, I often need to modify field values via reflection. I came across a great Stack Overflow answer worth documenting.

Gson User Guide

Mon, 08 Jun 2015 12:37:45 +0000

This article is compiled from the official Gson User Guide. Gson’s performance is competitive with other JSON frameworks, and being Google-maintained makes it a solid choice for Java/Android JSON processing.

Gson is a Java library developed by Google for serializing Java objects to JSON and deserializing JSON strings back to Java objects.

Cache Algorithms

Tue, 05 May 2015 16:31:28 +0000

Cache replacement policies determine which entries to evict when the cache is full. They have a direct impact on system performance. Here is an overview of common cache eviction algorithms.

Design Patterns

Mon, 30 Mar 2015 10:08:26 +0000

Design Patterns are reusable solutions to common problems in object-oriented design. The 23 classic patterns were systematized by the Gang of Four (GoF: Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides) in their 1994 book Design Patterns: Elements of Reusable Object-Oriented Software.

This article is compiled from a blog post by smallnest and a StackOverflow discussion on GoF design pattern implementations in the Java API.

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How Java HashMap Works Internally

Sat, 27 Dec 2014 08:35:07 +0000

HashMap is one of the most frequently asked topics in Java interviews — it effectively tests a candidate’s understanding of data structures and engineering trade-offs. This article breaks down its core design and implementation details.

Android EBUSY Exception

Mon, 22 Dec 2014 15:35:07 +0000

While working on an image upload feature, I encountered a runtime exception on certain devices:

java.io.FileNotFoundException: /mnt/sdcard/Android/data/com.xxxxxx.android/files/xxxx
    open failed: EBUSY (Device or resource busy)
    at libcore.io.IoBridge.open(IoBridge.java:406)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
    ...
    Caused by: libcore.io.ErrnoException: open failed: EBUSY (Device or resource busy)
    at libcore.io.Posix.open(Native Method)
    at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
    ...

Tencent Interview

Mon, 08 Dec 2014 10:35:07 +0000

I came across stormzhang’s Tencent interview questions and decided to work through them, documenting my answers and thought process.

Topics covered:

Android fundamentals (processes, Activities, Handler)
Screen density and resource qualifiers
Thread synchronization in Java
System design (resumable downloads, network architecture)

Lambda Expressions in Java 8

Sun, 07 Dec 2014 15:35:07 +0000

What is a Lambda Expression?

Lambda expressions are a core feature introduced in Java 8, enabling more concise code. Here is the most straightforward example:

Runnable runnable1 = new Runnable() {
    @Override
    public void run() {
        System.out.println("runnable1 start!!!");
    }
};
Runnable runnable2 = () -> System.out.println("runnable2 start!!!");

runnable1.run();
runnable2.run();

Both blocks are equivalent, but the lambda version is a single line. The basic form is () -> expression or () -> { statements; }.