Android设计模式系列(6)--SDK源码之享元模式

class SQLiteCompiledSql {
    private String mSqlStmt = null;
    native_compile(sql);
    native_finalize();
}

public class SQLiteDatabase{
     Map<String, SQLiteCompiledSql> mCompiledQueries = Maps.newHashMap();
     SQLiteCompiledSql getCompiledStatementForSql(String sql) {
        SQLiteCompiledSql compiledStatement = null;
        boolean cacheHit;
        synchronized(mCompiledQueries) {
            if (mMaxSqlCacheSize == 0) {
                return null;
            }
            cacheHit = (compiledStatement = mCompiledQueries.get(sql)) != null;
        }
        if (cacheHit) {
            mNumCacheHits++;
        } else {
            mNumCacheMisses++;
        }
        return compiledStatement;
    }
 
    private void deallocCachedSqlStatements() {
        synchronized (mCompiledQueries) {
            for (SQLiteCompiledSql compiledSql : mCompiledQueries.values()) {
                compiledSql.releaseSqlStatement();
            }
            mCompiledQueries.clear();
        }
    }
 
    void addToCompiledQueries(String sql, SQLiteCompiledSql compiledStatement) {
         //省略具体代码
    }
}