依赖Hutool-core

<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-core</artifactId>
    <version>5.3.8</version>
</dependency>

代码

import cn.hutool.core.util.ArrayUtil;
import org.junit.Test;
import cn.hutool.core.math.Combination;

public class ZuheTest {
    @Test
    public void zuhe() {
        Combination combination = new Combination(new String[]{"1", "2", "1", "4", "5"});
        List<String[]> rs = combination.select(3);//这个是待组合个数
        rs.forEach(o -> System.out.println(ArrayUtil.toString(o)));
    }
}

结果

[1, 2, 1]
[1, 2, 4]
[1, 2, 5]
[1, 1, 4]
[1, 1, 5]
[1, 4, 5]
[2, 1, 4]
[2, 1, 5]
[2, 4, 5]
[1, 4, 5]

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