[Android]開發技巧 靜態常數宣告

Use Static Final For Constants

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Consider the following declaration at the top of a class:

static int intVal = 42;
static String strVal = "Hello, world!";

The compiler generates a class initializer method, called , that is executed when the class is first used. The method stores the value 42 into intVal, and extracts a reference from the classfile string constant table forstrVal. When these values are referenced later on, they are accessed with field lookups.

We can improve matters with the "final" keyword:

static final int intVal = 42;
static final String strVal = "Hello, world!";

The class no longer requires a  method, because the constants go into static field initializers in the dex file. Code that refers to intVal will use the integer value 42 directly, and accesses to strVal will use a relatively inexpensive "string constant" instruction instead of a field lookup.

靜態常數宣告 盡可能使用 Final以減少 field lookup的動作, 而是直接參照 "字串常數".

官方文件：http://developer.android.com/training/articles/perf-tips.html