CODE:

package nice.cacheclear;

import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;

import android.app.Activity;
import android.os.Bundle;

public class CacheClear extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    	try {
    		Process p = Runtime.getRuntime().exec("su");
    		DataOutputStream dos = new DataOutputStream(p.getOutputStream());
    		dos.writeBytes("rm /data/data/com.android.browser/cache/webviewCache/*\n"); // ここでエラー
    		dos.writeBytes("rm /data/data/com.android.browser/app_thimbnails/*\n");
    		dos.writeBytes("rm /data/data/com.android.browser/databases/webviewCache.db\n");
    		dos.writeBytes("exit\n");
    	} catch (IOException e) {
    		e.printStackTrace();
    	}

        return;
    }
}

CODE:

public class CacheClear extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        deleteFiles("/data/data/com.android.browser/cache/webviewCache/");
        deleteFiles("/data/data/com.android.browser/app_thimbnails/");
    	deleteFiles("/data/data/com.android.browser/databases/webviewCache.db");
    }

    private boolean deleteFiles(String filePath) {
        boolean result = true; 
        File dFile = new File(filePath);

        if (dFile.isDirectory()) {
            String[] children = dFile.list();
            File targetFile;
            for (String currentFileString: children) {  // ここでエラー
                targetFile = new File(dFile, currentFileString);
                result &= targetFile.delete();  
            }  
        } else {
            result &= dFile.delete();
        }

        return result;
    }
}