join() または implode()

配列にjoin()メソッドがあるといいな…と思ったので。*1

Java版join() (配列)

public class Hoge {

  public static void main(String args) throws Exception {

    String array1 = {"aaa", "bbb", "ccc"};

    String array2 = {"111", null, "333", ""};

    String array3 = null;
    System.out.println("array1: [" + join(array1, ", ") + "]");

    System.out.println("array2: [" + join(array2, " AND ") + "]");

    System.out.println("array3: [" + join(array3, " : ") + "]");

  }
  public static String join(Object[] array, String sep) {

    if(array == null) {

      return null;

    } else if(array.length < 1) {

      return "";

    } else if(array.length < 2) {

      return (array[0] != null) ? array[0].toString() : "";

    }
    StringBuffer buf = new StringBuffer((array[0] != null) ? array[0].toString() : "");
    for(int i=1; i

実行結果は次の通り。


array1: [aaa, bbb, ccc]

array2: [111 AND  AND 333 AND ]

array3: [null]

Java版join() (リスト)

インターフェースを拡張したほうがよいのかな…？

import java.util.Arrays;

import java.util.List;
public class Hoge2 {

  public static void main(String args) throws Exception {

    List list1 = Arrays.asList(new String{"aaa", "bbb", "ccc"});

    List list2 = Arrays.asList(new String[]{"111", null, "333", ""});

    List list3 = null;
    System.out.println("list1: [" + join(list1, ", ") + "]");

    System.out.println("list2: [" + join(list2, " AND ") + "]");

    System.out.println("list3: [" + join(list3, " : ") + "]");

  }
  public static String join(List list, String sep) {

    if(list == null) {

      return null;

    } else if(list.size() < 1) {

      return "";

    } else if(list.size() < 2) {

      return (list.get(0) != null) ? list.get(0).toString() : "";

    }
    StringBuffer buf = new StringBuffer((list.get(0) != null) ? list.get(0).toString() : "");
    for(int i=1; i

*1:Commonsにあるかも