1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.io;
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3 |
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4 | import java.io.BufferedInputStream;
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5 | import java.io.BufferedOutputStream;
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6 | import java.io.File;
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7 | import java.io.FileInputStream;
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8 | import java.io.FileOutputStream;
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9 | import java.io.IOException;
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10 | import java.nio.charset.StandardCharsets;
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11 | import java.util.concurrent.TimeUnit;
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12 |
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13 | import org.openstreetmap.josm.Main;
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14 |
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15 | /**
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16 | * Use this class if you want to cache and store a single file that gets updated regularly.
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17 | * Unless you flush() it will be kept in memory. If you want to cache a lot of data and/or files, use CacheFiles.
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18 | * @author xeen
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19 | * @param <T> a {@link Throwable} that may be thrown during {@link #updateData()},
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20 | * use {@link RuntimeException} if no exception must be handled.
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21 | * @since 1450
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22 | */
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23 | public abstract class CacheCustomContent<T extends Throwable> {
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24 |
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25 | /** Update interval meaning an update is always needed */
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26 | public static final int INTERVAL_ALWAYS = -1;
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27 | /** Update interval meaning an update is needed each hour */
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28 | public static final int INTERVAL_HOURLY = (int) TimeUnit.HOURS.toSeconds(1);
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29 | /** Update interval meaning an update is needed each day */
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30 | public static final int INTERVAL_DAILY = (int) TimeUnit.DAYS.toSeconds(1);
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31 | /** Update interval meaning an update is needed each week */
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32 | public static final int INTERVAL_WEEKLY = (int) TimeUnit.DAYS.toSeconds(7);
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33 | /** Update interval meaning an update is needed each month */
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34 | public static final int INTERVAL_MONTHLY = (int) TimeUnit.DAYS.toSeconds(28);
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35 | /** Update interval meaning an update is never needed */
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36 | public static final int INTERVAL_NEVER = Integer.MAX_VALUE;
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37 |
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38 | /**
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39 | * Where the data will be stored
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40 | */
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41 | private byte[] data;
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42 |
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43 | /**
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44 | * The ident that identifies the stored file. Includes file-ending.
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45 | */
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46 | private final String ident;
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47 |
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48 | /**
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49 | * The (file-)path where the data will be stored
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50 | */
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51 | private final File path;
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52 |
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53 | /**
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54 | * How often to update the cached version
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55 | */
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56 | private final int updateInterval;
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57 |
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58 | /**
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59 | * This function will be executed when an update is required. It has to be implemented by the
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60 | * inheriting class and should use a worker if it has a long wall time as the function is
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61 | * executed in the current thread.
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62 | * @return the data to cache
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63 | * @throws T a {@link Throwable}
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64 | */
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65 | protected abstract byte[] updateData() throws T;
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66 |
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67 | /**
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68 | * Initializes the class. Note that all read data will be stored in memory until it is flushed
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69 | * by flushData().
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70 | * @param ident ident that identifies the stored file. Includes file-ending.
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71 | * @param updateInterval update interval in seconds. -1 means always
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72 | */
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73 | public CacheCustomContent(String ident, int updateInterval) {
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74 | this.ident = ident;
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75 | this.updateInterval = updateInterval;
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76 | this.path = new File(Main.pref.getCacheDirectory(), ident);
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77 | }
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78 |
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79 | /**
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80 | * This function serves as a comfort hook to perform additional checks if the cache is valid
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81 | * @return True if the cached copy is still valid
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82 | */
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83 | protected boolean isCacheValid() {
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84 | return true;
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85 | }
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86 |
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87 | private boolean needsUpdate() {
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88 | if (isOffline()) {
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89 | return false;
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90 | }
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91 | return Main.pref.getInteger("cache." + ident, 0) + updateInterval < TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())
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92 | || !isCacheValid();
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93 | }
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94 |
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95 | private boolean isOffline() {
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96 | try {
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97 | checkOfflineAccess();
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98 | return false;
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99 | } catch (OfflineAccessException e) {
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100 | Main.trace(e);
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101 | return true;
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102 | }
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103 | }
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104 |
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105 | protected void checkOfflineAccess() {
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106 | // To be overriden by subclasses
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107 | }
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108 |
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109 | /**
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110 | * Updates data if required
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111 | * @return Returns the data
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112 | * @throws T if an error occurs
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113 | */
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114 | public byte[] updateIfRequired() throws T {
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115 | if (needsUpdate())
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116 | return updateForce();
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117 | return getData();
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118 | }
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119 |
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120 | /**
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121 | * Updates data if required
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122 | * @return Returns the data as string
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123 | * @throws T if an error occurs
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124 | */
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125 | public String updateIfRequiredString() throws T {
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126 | if (needsUpdate())
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127 | return updateForceString();
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128 | return getDataString();
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129 | }
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130 |
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131 | /**
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132 | * Executes an update regardless of updateInterval
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133 | * @return Returns the data
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134 | * @throws T if an error occurs
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135 | */
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136 | public byte[] updateForce() throws T {
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137 | this.data = updateData();
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138 | saveToDisk();
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139 | Main.pref.putInteger("cache." + ident, (int) (TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())));
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140 | return data;
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141 | }
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142 |
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143 | /**
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144 | * Executes an update regardless of updateInterval
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145 | * @return Returns the data as String
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146 | * @throws T if an error occurs
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147 | */
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148 | public String updateForceString() throws T {
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149 | updateForce();
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150 | return new String(data, StandardCharsets.UTF_8);
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151 | }
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152 |
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153 | /**
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154 | * Returns the data without performing any updates
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155 | * @return the data
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156 | * @throws T if an error occurs
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157 | */
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158 | public byte[] getData() throws T {
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159 | if (data == null) {
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160 | loadFromDisk();
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161 | }
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162 | return data;
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163 | }
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164 |
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165 | /**
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166 | * Returns the data without performing any updates
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167 | * @return the data as String
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168 | * @throws T if an error occurs
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169 | */
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170 | public String getDataString() throws T {
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171 | byte[] array = getData();
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172 | if (array == null) {
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173 | return null;
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174 | }
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175 | return new String(array, StandardCharsets.UTF_8);
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176 | }
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177 |
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178 | /**
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179 | * Tries to load the data using the given ident from disk. If this fails, data will be updated, unless run in offline mode
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180 | * @throws T a {@link Throwable}
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181 | */
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182 | private void loadFromDisk() throws T {
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183 | try (BufferedInputStream input = new BufferedInputStream(new FileInputStream(path))) {
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184 | this.data = new byte[input.available()];
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185 | if (input.read(this.data) < this.data.length) {
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186 | Main.error("Failed to read expected contents from "+path);
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187 | }
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188 | } catch (IOException e) {
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189 | Main.trace(e);
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190 | if (!isOffline()) {
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191 | this.data = updateForce();
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192 | }
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193 | }
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194 | }
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195 |
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196 | /**
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197 | * Stores the data to disk
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198 | */
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199 | private void saveToDisk() {
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200 | try (BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(path))) {
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201 | output.write(this.data);
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202 | output.flush();
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203 | } catch (IOException e) {
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204 | Main.error(e);
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205 | }
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206 | }
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207 |
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208 | /**
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209 | * Flushes the data from memory. Class automatically reloads it from disk or updateData() if required
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210 | */
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211 | public void flushData() {
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212 | data = null;
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213 | }
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214 | }
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