回答編集履歴
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@@ -1,3 +1,107 @@
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args.lengthが0の時にifを実行してメッセージを表示しても、それ以降のコードは普通に実行してしまいます。
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なので、args.length==0の場合を抜けるときにreturnしてmainメソッドから抜けてしまうか、続くコードをelseブロックにしてとにかくargs.length==0の時に`args[0]`にアクセスしないようにしないといけません。
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```java
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public class NameOfMonths {
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public static void main(String[] args) {
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String[] month;
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month = new String[]{"January","February","March","April",
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"May","June","July","August","September","October",
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"November","December"};
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if(args.length == 0) {
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System.out.println("使用方法: java NamesOfMonths <number>");
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return; //ここでmainメソッドから抜ける
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}
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int i = Integer.parseInt(args[0]);
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if(i>12){
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System.out.println("引数には、１～１２の範囲の整数を指定してください");
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System.out.println("使用方法: java NamesOfMonths <number>");
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}else{
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System.out.println(month[i-1]);
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}
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}
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}
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```
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```java
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public class NameOfMonths {
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public static void main(String[] args) {
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String[] month;
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month = new String[]{"January","February","March","April",
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"May","June","July","August","September","October",
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"November","December"};
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if(args.length == 0) {
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System.out.println("使用方法: java NamesOfMonths <number>");
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} else { // args.lengthが0の時にこれ以降を通らないようにする
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int i = Integer.parseInt(args[0]);
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if(i>12){
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System.out.println("引数には、１～１２の範囲の整数を指定してください");
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System.out.println("使用方法: java NamesOfMonths <number>");
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}else{
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System.out.println(month[i-1]);
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}
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}
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}
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104
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}
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106
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107
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```
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