Java HashMap

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Java Hashmap Tutorial and Examples.

Quick Java HashMap Examples and HowTos

1. Putting Mime Types in a Hashmap
public class ContentTypeUtil {

    private static final Map<String, String> mimeMap;

    static {
        mimeMap=new HashMap<String, String>();
        mimeMap.put("jpg","image/jpeg");
        mimeMap.put("gif","image/gif");
        mimeMap.put("bmp","image/bmp");
        mimeMap.put("png","image/png");

    }

}

You can also put extensions in a HashMap:

private static final Map<String, String> extMap;

    static {
        extMap=new HashMap<String, String>();

        extMap.put("image/jpeg", ".jpg");
        extMap.put("image/gif", ".gif");
        extMap.put("image/bmp", ".bmp");
        extMap.put("image/png", ".png");
        extMap.put("image/cis-cod", ".cod");
        extMap.put("image/gif", ".gif");
        extMap.put("image/ief", ".ief");

        extMap.put("image/pipeg", ".jfif");
        extMap.put("image/svg+xml", ".svg");
        extMap.put("image/tiff", ".tif");
        extMap.put("image/x-cmu-raster", ".ras");
        extMap.put("image/x-cmx", ".cmx");
        extMap.put("image/x-icon", ".ico");
        extMap.put("image/x-portable-anymap", ".pnm");
        extMap.put("image/x-portable-bitmap", ".pbmv");
        extMap.put("image/x-portable-graymap", ".pgm");
        extMap.put("image/x-portable-pixmap", ".ppm");
        extMap.put("image/x-rgb", ".rgb");
        extMap.put("image/x-xbitmap", ".xbm");
        extMap.put("image/x-xpixmap", ".xpm");
        extMap.put("image/x-xwindowdump", ".xwd");

        extMap.put("video/mpeg",".mpeg");
        extMap.put("video/quicktime",".mov");
        extMap.put("video/x-la-asf",".lsf");
        extMap.put("video/x-la-asf",".lsx");
        extMap.put("video/x-ms-asf",".asf");
        extMap.put("video/x-ms-asf",".asr");
        extMap.put("video/x-ms-asf",".asx");
        extMap.put("video/x-msvideo",".avi");
        extMap.put("video/x-sgi-movie",".movie");
        extMap.put("video/mp4",".mp4");

    }
2. Search HashMap keys

For example we can search the media file extensions that we had populated into our HashMap above.

To search a HashMap you use the containsKey() method. Once we've found the key we use it to get the value which is the actual extension.

    public static String getExt(String contentType) {
        if(contentType==null){
            return "";
        }
        contentType=contentType.toLowerCase().trim().replaceAll(" +", " ");
        if(!extMap.containsKey(contentType)){
            return "";
        }

        String ext = extMap.get(contentType);
        return ext;

    }

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About Me.

After completing his Software Engineering bachelors program, Oclemy(Clement Ochieng) these days is a man of two lives. At day he works for a startup in Nairobi, Kenya. At night he works tirelessly on building ProgrammingWizards TV, a tv channel for student coders and this website to help share the source code. In between he practices Meditation and Self actualization to help him keep balance. He also likes going for long solo walks to connect more with nature.




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