回答編集履歴
1
コード
test
CHANGED
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@@ -87,3 +87,117 @@
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87
87
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map.computeIfAbsent(catName, Category::new).increment();
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88
88
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89
89
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```
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90
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91
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92
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93
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---
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94
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95
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96
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97
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私が作るなら、クラスはCarだけで十分で、まあ実行用クラスとしてCSVInandOutは作るとして、こうなります。
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98
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99
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```java
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100
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101
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public class Car {
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102
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103
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final String name; //車名
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104
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105
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final String company; //メーカー
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106
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107
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final String catname; //車種
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108
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109
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110
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111
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//Carクラスに追加したコンストラクタ
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112
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113
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Car(String name, String company, String catname){
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114
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115
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System.out.println("Carクラスのコンストラクタが呼びだされました");
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116
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117
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this.name = name;
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118
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119
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this.company = company;
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120
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121
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this.catname = catname;
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122
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123
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}
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124
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125
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126
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127
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@Override
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128
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129
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public String toString() {
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130
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131
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return name + "," + company + "," + catname;
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132
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133
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}
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134
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135
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}
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136
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137
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```
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138
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139
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```java
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140
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141
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// import省略
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142
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143
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public class CSVInandOut {
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144
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145
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public static void main(String[] args) {
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146
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147
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List<Car> carList = new ArrayList<Car>(); //データ格納用リスト
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148
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149
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Map<String, Integer> cat_num = new HashMap<>();
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150
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151
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String input = "carIn.csv";
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152
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153
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String output = "carOut.csv";
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154
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155
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156
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157
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try(BufferedReader InputLine = new BufferedReader(new FileReader(input));
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158
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159
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PrintWriter outputLine = new PrintWriter(new FileWriter(output))) {
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160
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161
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162
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163
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String line;
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164
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165
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166
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167
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line = InputLine.readLine(); //ヘッダの読み書き
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168
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169
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outputLine.println(line);
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170
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171
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172
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173
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//1行ずつ読み込み
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174
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175
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while ((line = InputLine.readLine()) != null) { //String変数lineに格納
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176
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177
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String[] st = line.split(","); //lineを分割の対象にする
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178
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179
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Car car = new Car(st[0], st[1], st[2]);
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180
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181
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carList.add(car); //リストに追加する
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182
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183
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cat_num.marge(car.catname, 1, Integer::sum);
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184
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185
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outputLine.println(car);
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186
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187
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}
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188
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189
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190
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191
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}
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192
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193
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catch (IOException e) {
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194
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195
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System.out.println("ファイルが開けません");
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196
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197
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}
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198
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199
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}
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200
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201
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}
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202
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203
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```
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