关于java:获取数组列表中元素的两两组合

创立两两组合实体类

@Data@NoArgsConstructor@AllArgsConstructorpublic class MaterialRelevance {    /**     * 编码1     */    private String code1;    /**     * 编码2     */    private String code2;}

获取两两组合

    /**     * 获取一个数组中两两组合     *     * @param list     * @return     */    public List<MaterialRelevance> combineTwoElement(List<String> list) {        List<MaterialRelevance> resultList = Lists.newArrayListWithExpectedSize(list.size() * list.size() / 2);        if (CollectionUtils.isEmpty(list)) {            return null;        }        if (list.size() >= 2) {            for (int j = 0; j < list.size(); j++) {                resultList.addAll(ll(list.subList(j, list.size())));            }        }        return resultList;    }    private List<MaterialRelevance> ll(List<String> list) {        List<MaterialRelevance> resultList = Lists.newArrayListWithExpectedSize(list.size() * list.size() / 2);        for (int j = 1; j < list.size(); j++) {            resultList.add(new MaterialRelevance(list.get(0), list.get(j)));        }        return resultList;    }