Category Archives: StudyNotes

Two Hidden Bugs of Conditional Operators

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Programmers create bugs, but experienced programmers should be familiar with their language and have best practices to avoid possible common bugs. I found operators are sometimes easy to behave weirdly. Today I memo two bugs to help readers and myself avoid them in the future. == has higher precedence than && and ||… Read more »

Difference between Redirection and Pipe in Linux

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Now and then, I meet symbols such as >, >>, &&, ||, and  | between Linux commands in CLI. Every time I had a hard time recalling the concepts and difference between Redirection and Pipe, I wanted to write a short but to-the-point summary of it. Simple but astonishing idea… Read more »

Distributed Database Review 1: Oracle RAC

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I found some typical structures of distributed database systems and I want to write short reviews in the following posts. Database systems on a single machine suffers from low availability (single point failure), low concurrency (one query per core), low reliability (no replication) and low scalability (computing resources limitation). Therefore… Read more »

Metadata of an Android App – AndroidManifest.xml and build.gradle

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AndroidManifest.xml and build.gradle Metadata of the app. Icons, App name, theme, entry Activity are all configured here. Icon Icons are png files which have five different dpis. In Package view, Icons can be located at mipmap-mdpi, mipmap-hdpi, mipmap-xhdpi, mipmap-xxhdpi, mipmap-xxxhdpi. Remember to replace them all or delete those unwanted. The… Read more »