文字列 と 配列,List の相互変換

変換前	変換後
List<Character>	String
String	ArrayList<Character>
char[]	String
String	char[]
StringBuilder	char[] （コピー）

もっと楽な方法ないのかな。

ConvertStringArrayList.java

import java.util.Iterator;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ConvertStringArrayList {
    public static void main(String[] args){
        ArrayList<Character> list = new ArrayList<Character>(Arrays.asList('h','e','l','l','o'));
        String str = "hello";
        char[] arr = {'h','e','l','l','o'};

        // ArrayList<Character> -> String
        if (toStr(list).equals(str)) System.out.println("OK");
        else System.out.println("not OK");
        // String -> ArrayList<Character>
        if (toList(str).equals(list)) System.out.println("OK");
        else System.out.println("not OK");
        // char[] -> String
        if (new String(arr).equals(str)) System.out.println("OK");
        else System.out.println("not OK");
        // String -> char[]
        if (Arrays.equals(toArr(str),arr)) System.out.println("OK");
        else System.out.println("not OK");

        // StringBuilder -> char[] (コピー)
        StringBuilder sb = new StringBuilder("hello");
        char[] arr3 = new char[5];
        sb.getChars(0,sb.length(),arr3,0);
        if (Arrays.equals(arr3,arr)) System.out.println("OK");
        else System.out.println("not OK");
    }   

    public static String toStr(List<Character> list){
        // List<Character> -> String
        int l = list.size();
        char[] cs = new char[l];
        Iterator<Character> iter = list.iterator();
        for (int i=0;i<l;i++) cs[i] = iter.next();
        return new String(cs);
    }   

    public static ArrayList<Character> toList(String str){
        // String -> ArrayList<Character>
        int l = str.length();
        ArrayList<Character> list = new ArrayList<Character>();
        for (int i=0;i<l;i++) list.add(str.charAt(i));
        return list;
    }   

    public static char[] toArr(String str){
        // String -> char[]
        int l = str.length();
        char[] arr = new char[l];
        for (int i=0;i<l;i++) arr[i] = str.charAt(i);
        return arr;
    }
}