随机密码生成

编写一个函数，用于生成随机密码，入参为随机密码的长度，出参为生成的随机密码，要求生成的随机密码必须同时包含大写字母小写字母数字。

V1（低效）:

import java.util.Random;

public class Main {
    public static void main(String[] args) {
        while (true)
            System.out.println(randomPW(6));
    }

    public static String randomPW(int pwLen) {
        // 长度至少为3
        if (pwLen < 3) return null;

        char[] cArr = new char[pwLen];

        // 随机设置数字字符数量
        int numLen = new Random().nextInt(pwLen - 2) + 1;
        // 随机设置大写字母字符数量
        int upperCaseLetterLen = new Random().nextInt(pwLen - numLen - 1) + 1;
        // 设置小写字母字符数量
        int lowerCaseLetterLen = pwLen - numLen - upperCaseLetterLen;

        for (int i = 0; i < numLen; i++) {
            int randomPos;
            // 算法瓶颈在于这个while循环可能要花费较长的时间找到一个合适位置
            while (cArr[randomPos = new Random().nextInt(pwLen)] != '\0') {
                ;
            }
            cArr[randomPos] = (char) ('0' + new Random().nextInt(10));
        }
        for (int i = 0; i < upperCaseLetterLen; i++) {
            int randomPos;
            // 算法瓶颈在于这个while循环可能要花费较长的时间找到一个合适位置
            while (cArr[randomPos = new Random().nextInt(pwLen)] != '\0') {
                ;
            }
            cArr[randomPos] = (char) ('A' + new Random().nextInt(26));
        }
        for (int i = 0; i < lowerCaseLetterLen; i++) {
            int randomPos;
            // 算法瓶颈在于这个while循环可能要花费较长的时间找到一个合适位置
            while (cArr[randomPos = new Random().nextInt(pwLen)] != '\0') {
                ;
            }
            cArr[randomPos] = (char) ('a' + new Random().nextInt(26));
        }

        return String.valueOf(cArr);
    }
}

V2（高效）:

import java.util.Random;

public class Main {
    public static void main(String[] args) {
        while (true) {
            System.out.println(randomPW(6));
        }
    }

    public static String randomPW(int pwLen) {
        // 长度至少为3
        if (pwLen < 3) return null;

        char[] cArr = new char[pwLen];

        // 随机设置数字字符数量
        int numLen = new Random().nextInt(pwLen - 2) + 1;
        // 随机设置大写字母字符数量
        int upperCaseLetterLen = new Random().nextInt(pwLen - numLen - 1) + 1;
        // 设置小写字母字符数量
        int lowerCaseLetterLen = pwLen - numLen - upperCaseLetterLen;

        int[] randomPos = getRandomSequence(pwLen);

        // 依照生成的随机序列散列三种字符
        for (int i = 0; i < pwLen; i++) {
            if (i < numLen)
                cArr[randomPos[i]] = (char) ('0' + new Random().nextInt(10));
            else if (i < numLen + upperCaseLetterLen)
                cArr[randomPos[i]] = (char) ('A' + new Random().nextInt(26));
            else if (i < numLen + upperCaseLetterLen + lowerCaseLetterLen)
                cArr[randomPos[i]] = (char) ('a' + new Random().nextInt(26));
        }

        return String.valueOf(cArr);
    }

    // 高效的随机序列生成算法（0 ~ pwLen）
    public static int[] getRandomSequence(int pwLen) {
        int[] input = new int[pwLen];
        int[] output = new int[pwLen];

        for (int i = 0; i < pwLen; i++) {
            input[i] = i;
        }

        int end = pwLen;

        Random random = new Random();

        for (int i = 0; i < pwLen; i++) {
            int temp = random.nextInt(end);

            output[i] = input[temp];
            input[temp] = input[end - 1];
            end--;
        }

        return output;
    }
}

1s0ywS	zrD912	0Bmgaf	LM3Vxe	D3I3My	0pFxrz	1tlwrJ	A1Ae68	Le9151	403dL4
48d2UM	dgF7i0	i2H335	oZ1PNO	9t28P2	6e0UGd	n61e0W	auA4LM	2741wX	Vf44VF
4Om5os	5N389c	BaQM5R	ze2Jpe	FWVu3R	XQdV91	zx78Nx	dONM4P	zHi1ly	aS0tm8
2G7f01	MJc0k4	I883pH	oe40RK	fY0gVn	2h98YQ	h2S560	qoGhj6	nOKh68	QXyS8P
AMY3g2	OQuY05	a0482G	Z8OMy3	9QbG55	u6i8I7	R8qRzu	Uts7hS	jA0L0P	mm97Pk
lv7M4z	267Qi0	yPa80f	4g4vzM	g8TB7Q	FY3ZeW	3yRs90	B34k94	Bvl6vp	1rzkiA
kAbn2k	b4KRxd	Dm6BnE	7hRJc2	4768Zr	b361wN	12faWn	6807Wb	5Pxs19	k7241B
f254Lo	5i4D08	1kX71n	05bHX7	o6Q9HT	v3Q608	43F04m	0mj27C	4T192d	6Es1X6
8CJNws	2Yp06I	9Yok95	6j67gT	r1tB1y	641h4E	Z36bf6	3jr9hG	3dJ54x	jFf0vs
50gXZ7	j3249B	M7U33l	y99T9n	4XOVv8	vB1A27	6aK835	0IA98g	0psF9k	oAKE36
u7bfqH	HvJZ5x	ow1fQ4	5y6O7p	46V78l	08E1vM	PV6JOz	w3cNZg	2oV59j	aA15fb
Pk04Lb	1o25R7	5fJs8q	JNx59g	9fqvcA	f68Iz8	nMz20u	yCN7lD	uZSm4H	n4918Y
38Fz3W	5TVV2n	Jn508P	Y4fwof	2188fU	QXXx67	Rj9IC4	0LPM7v	K3uT7D	x26l5V
8W71a6	cBK1Va	ZD4BjI	IcfSz2	8088Jx	N801q0	AcID06	F1Qfx5	65bTll	haIu5D
e5iR5M	YkjY6C	85Xkh3	46Q3gp	s4X828	06Ks4m	750H4z	438vH1	pwQ07j	PfNSQ6
c1oNkS	sgd26L	1sB31s	n1g0D3	OY9cU1	b7oW5t	x446Ck	Ss6Nzu	g46I43	oOQ42E
3Z44j1	Ol6bou	qR4812	p2wVt5	7cKeac	z4c18P	KL0NnF	sPe9ce	2D8v49	vOwl48
F2k335	x0rIP3	ryXrn7	7yK80O	e4Pkes	9054kP	j505D7	1q7H79	2RNlet	ay25Ku
0G19Uv	t8PXc3	6ZfIdp	84Yhyh	Cu8173	f3KEhi	H3urff	2S4q87	o4OsE9	A04iJo
Jo4rWI	cV1qWB	eEsC7s	7c34aT	8Sm8YN	s93Yz6	pX0p6e	IH7y3Q	1e6Y25	865rP6
4H3ob7	BgKo6a	i4qP4E	v8x7bB	Ey89Yo	Re7427	5AZ26h	oU0ko0	b6E3vG	Hj9H6o
2y478D	9Td122	eJ4756	mu0ubP	H4zK0Z	oRZ25z	VmUk1y	A8KHJq	K93j59	mil8Pz
RPif70	2xKFTB	3W56z0	8mK411	93Hds6	0519Bk	if97RL	645e6S	712BxZ	1i53Z2
05k0O6	cWM9K3	8It71v	2y1A83	y98yXu	42Im1H	p2tHUR	V5AEs8	mL97Gc	5i2WJ7
6MUiHY	e08Az6	KVB0w4	j7GdOq	953Uz7	8Hs740	sP2LVy	sgGwc1	Z2DgjO	lA8VOG
Y1FLTw	4LTy52	7QJ8kg	z9X90S	ZB4brh	XL4s53	6Bq416	6dpQ4a	4C0c15	8l6Br4
u5U873	6n74F7	los4Dh	dl94GS	5p4BsB	556hI9	h7F302	A83w8K	Z9246k	3Wg5u5
1oAy47	0sWaie	rhNJA1	A4i63E	66eBwu	C84B0t	7GwOON	f31U1V	Im1649	So2uo7
r2B829	g3F9o5	DX9h8A	631zhC	U6uToJ	4nZf1Q	w3v1Xp	rdtw3N	h404L6	P941m8
6FcU2m	Z88Q8h	62wF59	2KfSnd	G35h55	NCgAE7	Zd58pe	W8O1nw	K673Me	r9KOi8
3ZAeq6	4bjb6W	1R3cUR	7SX4Zm	lRZ2Wn	9VX41l	ex6HtA	1nRgQ7	71d42T	1Rat6u
v639zF	yLtMq2	20lp0K	97H3jq	d305BQ	eL0kuH	kc0a4E	2v26iL	6eiJ7D	8T2pr7
85Ls7L	cwV27V	FV6r53	LydI5o	4o580P	4w960M	k4tuJ9	b7USEE	9S28z1	4145Cv
Pkh7p8	61P9i2	zJF3oF	i5SiNy	7t0S23	2A9n13	3CiW7s	8E4GAj	bG300p	T682l4
E888d9	kz4Vkf	n2puVa	Fa4swI	InDB3K	4fGjSM	F6aFFv	1iJyT2	BjguI0	VHn84s
s0G353	uY2eea	vrQ63E	AIw4AA	f3zTq8	nbG3x3	362gK3	ps2dF3	a9J30S	27FCCd
dYaE8k	i2007W	P5801p	60VgJ3	71guEr	61sGxv	ds8X5M	fH2T72	2f6F78	A3npyv
kBQ2e7	dOdq9n	9fV4XZ	7z1hLu	1623La	U6TsCj	FT5DAp	9Nr1K3	n5xwmL	4A9Mt5
748rGN	Q9h4M6	t74Q12	6qmG1b	9V16n0	j0Q325	R0yAqZ	95c8Mx	4xN4K8	1n035T
Hv5rSc	1T0n52	ylw8hN	736t6K	g8bPej	gdCs7d	03Lyz8	W383w0	P2196c	L5plxs
gpuKA5	6dVm5e	Wz6jJ0	3sFuj1	uNA0SX	ZW23hP	1I7wO2	2138dJ	758p9I	73G11n
bI52c7	74Dz68	T99U3o	fkK8nt	b6mTMW	C690n5	amF4z1	pCc9Zi	1Dn143	7W927r
9bv7CK	239Aw2	slJ5lq	8igUBX	21H7qY	cWpm34	Y8HA4j	2zu9Ww	l3BL58	32j99G
690Vw8	n2xxJ2	oOW6BH	77fA47	R43Kb4	7q730Z	1usz0T	498PIj	Y1q348	56G67t
e2438O	Ujs36E	kP6s30	68exG7	2kVsI4	fL6cv1	Qa8501	uQH113	r9D4pv	r967hT
D09i64	RVp0QU	9cZ0IY	aN4985	Yt67y7	fC7Y28	L9pb5c	I519b2	15i4Q6	DUK9hi
8KIxFx	yo41uQ	63hWEI	78lXqg	Hb901V	51cM05	05dVqv	F317z8	lZ5767	c5vArs
285Dc7	0Z73mq	y275ML	7188gV	428g0X	fP4RYD	zEu5Ba	c49A7f	1f27bM	s15aXy
57Zi19	2ka3Uo	9qX99K	O57bV9	8S5f8j	7N48aN	29Fkz8	6b8k8R	kgl0Ks	V3mypq
g6d4GG	9vH30c	o0PgAJ	0BQo5c	7xvtRs	lvJ6vK	Uzi9pR	z4X896	pHnYk9	8035Ye
B8CYf1	9wxtgI	93blCm	fXi8Of	H4Ro0B	1g3Y0b	Y5z1Pl	iQ5GCC	Wm9vqX	0eTZHH
o0YKO9	SepN2v	b8W72f	hTdjo3	28gxU3	A39j7s	RO6l85	Z5y194	ofvm5Y	wsfb2D
6H4e53	1z811B	Sj6jKZ	Tlc1xg	46nbdH	6R9nk3	4s545C	42rEdc	8995Pd	801j0A
e83I09	ar3J2S	Z951r6	usC2Y3	OT2ufx	EC89ad	k3d7GG	72q4O5	mY3d1r	4ar6ML
2M576s	f2jTUz	0G2Gcq	tjL4oA	d75U20	70Lf14	ALB3fz	56K52x	Cemj5q	Z433Yb
0j938V	V8UOw4	UnmRE9	83Z16d	97Ekgy	p3uTlw	IBg106	ys8n7P	DpBXf9	qwLf0s
1E57u4	39jnO2	vQm6u8	96ppMH	NxHqm0	a45D2R	03n1M9	w2V8O5	k25W1p	TZ302e
pW1tn4	fqxQ71	C5a73S	469fRk	GU8HTc	89eH67	7VaEbA	zz019M	V8g9Sy	O1qZrd
rV5CzX	z1w5Q2	g4037A	aW7Ovs	V8k5C1	32g10K	S8d5WH	1F060b	8U85a6	4YT9m0
eB9Pt2	nn3iQe	edO5c4	4cUD22	8F7w39	iC5ix9	8v9dMt	78P22b	28Oe57	eBTC28
Jd5921	V35s0U	Df95sK	dZ49G9	CP8Nx1	51i3B1	BSjo7h	6KJRcE	E9C7pN	8lTkxb
p0F1Uf	200c2O	7p238W	p9ELhm	t8TeBp	U44q19	N846bq	X1hp67	e1e1nA	w3Sn9v
DcSB1W	UhH2CN	23qtQv	k81yiO	3f61dW	53r4NC	b8M69N	4qA7M9	a9D670	R859i5
W604q1	c12L94	k391Y3	Q5fpal	HBn85B	D4jEFu	d6A4pn	9Pu653	Pwfes3	d2Uzlb
lkK7sL	j1519M	fQ7y42	K65wzw	d087Lb	6K6g1i	N4k1dq	670Ad0	h6v8TY	6R63q7
o8KLn0	06RF5l	5I900c	95SfEx	3Zy262	0rrVh4	yc3KlO	0G7OFl	04b02B	lNj24p
3P14i7	v1q96A	wr3dnK	bF6QZ1	8p8Ms4	73P8r5	rAg868	z03V2y	D9UGtJ	y2146I
G7ubI6	0NG3b8	V3VjpD	V3l50m	MDt5bN	A46UMh	NcF2LC	qU0Pnh	H5zrvf	983u0Q
1ml33Q	4Itq0L	u335D0	U6QbQG	0oT5XE	9sEHOq	5KEXoF	P69aES	07Hh72	44RUQl
2rK3bn	q0A5BV	R04u5W	ue9GMj	gGND9S	7Q523e	6nulX8	2ZeWr6	Pk8001	PV9ncQ
prU4Lq	Gn3717	1jG3Z8	T99g46	29Wc94	aqK9WZ	uX6zzc	1z7U32	60jB00	0u30AA
87MgbN	JyN1Yn	r13k2A	77Z41v	tVm3De	U85S3i	N7k344	S1Ouly	5Za7s6	AAk6Gp
3BBtWQ	544ATf	3tLX28	14X65a	KtA60C	771S2d	8368On	zf4d2Q	aE1703	ueCan6
F4M0jv	Am37l7	6g8O29	x654K7	Ed4378	n1V554	k57F78	5mUz79	F2i2Wd	0Py719
8s2BPS	3jaH6O	dZj233	z8413B	5y2R0y	u33YuH	V5IHvo	To9dBG	9C9jP7	bE75Yx
L9x579	n8iAOH	h69M9H	hjT037	K459m9	kpL68u	5671Nh	l332N4	e8JFQ1	BhZ0YV
Pk432y	OXNN8l	31O0yT	iccR6R	V2KZTt	6hwUIh	464Vk8	6Ts6e9	02u86Q	KwIj8M
52tApb	dTaz5m	7yLkTh	7vY282	Dz32H6	92gklO	6Z5Kf7	06aCQ0	oBI04O	1d4Gsg
3E6b87	3D775v	B1U8v7	91s62V	Xh6ouj	aiQ340	31b3A1	lOuN44	n211K5	FK1i50
VWFQp6	pu84I4	7O5h6O	AOFiP8	42Xxu7	t8256D	iID0al	gF38EQ	5bkqeH	00oGh5
9lBfpQ	s0340X	v1371Y	Q7jxaQ	x43xT3	vygs3W	g4gmXe	55Vu16	v7YX81	ZfQJV3
514UuU	94nIB7	FQ2n9w	L4qoiz	pZn8W7	n3ClY2	53U45s	EmG7WG	189kG5	D27Kay
8aPe55	Z0fJJV	j7eTgp	Q45eU6	0yTD70	ikP0E9	QJWx8l	P7BAuX	c3685V	w3avFK
U8bAAW	DqP2Od	832J8l	4GOsBI	k3J3fy	BkRn2M	n9Khak	4Fss97	p40Z1c	R8Y0Qh
9Rq768	1xp6gF	0592Nh	05zJ8T	9L5rCt	3f7M13	163eTs	cQ6FGZ	xHH56m	HGwPH8
7zG6w6	Zqi6CE	6990Us	Grm470	t80KYB	hQoik4	1kR917	vGm527	GRkFt5	i7xzVT
Snb5Ep	1Nl7m5	Suo26d	E5kf0k	U015n2	M0juQg	14v03Y	z725H8	A41bd1	6X6ryV
99sISm	AVfQ4D	Y3PnIM	o4Bc38	eAj1p9	2zpAHt	O94t5N	0q286M	57O74f	3alX51
oQNX3d	ru2L87	x8799L	JdNxn3	4Y2k07	6g96Rl	6X123f	i0r4MX	D9v1iM	SGfBF2
1I94l6	5J269w	x6YRyV	dDY9S1	o7E9sp	Ia63JF	IaNPa3	6oU1m2	6751yP	r6EkFW
WKff6b	i5Fq26	4r6B0k	W3CuLP	w1fpW9	1K9TRd	o9H87c	ri3mjS	3In8ZZ	WL86c1
A1ZOwr	OCqhg9	Eu9e4a	sHm66X	911y6S	5Sa05d	48T35g	I5Rjox	G2fXnd	0j796W
A84S4o	g34WzD	4Yy91L	5T5r10	0039Oh	f5SU9G	8z3xmE	s4n3K8	cGk41S	52u1R9
040s9A	ndE2xe	lB1ozh	v7jO1o	P7Hf3x	3186Ei	t5T117	z4S370	7943pR	N2fS4S
157P9p	mm8P3W	yEXg3M	DK6cb1	u35evA	xeR6pj	4nAuYM	1tRCTp	8k53S2	m8D485
V7RiN9	9dH221	P0Ksv0	L40bwr	tQs630	31mW4W	T71Px8	s3KVP2	aV103Z	4983sG
e83IJJ	gP1394	Enb8Xv	H06luG	Cd97tq	J5642e	il5JM6	2sfI49	KXc1xK	XFU9iY
sV2uWq	wG88e5	K841a8	3A8g48	t8D38n	oR4LWZ	h3K3vs	W297j1	6g77Rb	Zab9wa
4r3U68	1pEw4f	J1d941	T9xpmT	2P12tH	95Ms21	y6Nl8U	S1f1K4	5dZ424	5P9rhe
WhwMe5	Dbda9x	J7003m	8ySQ5H	1loVMS	hF16Ge	3sL8NR	ldysZ7	2R7LCc	N966y0
N2L6Wv	3C12l8	Mo0FGR	7J2tU6	a9Vd9S	EFrWQ4	f6Tgxf	94kaM9	Dqsyj2	VyUf0S
vmW378	tjS583	0tkVjo	1P8oj4	6P660g	5emrU1	514h9A	HtJ6mb	H6b3U4	77F4vn
t9B81P	e6B452	lYJ2Py	c3tr8Q	QzSX2J	dY8v0O	p977P3	85ccJ1	4B7s15	9L2g14
474woP	9IgwQr	9NRll7	C86vvm	07I31c	NM688b	77gMNE	fHX433	ctA346	o656W6
49kyVH	K5sbDu	0Q4qc4	2O9c14	dgZ3V9	xGY534	Vs7ba4	JD5f6l	3j75A7	f0Z8J9
D0h77d	9Eev4J	ek14JQ	Ib61mq	qYd317	495J6c	aN7Cz6	PkaO3G	Aa9L72	511wR4
qK12v0	o34WK0	Sgw4E9	h98J93	X46h99	z27P88	883Xw3	f6B308	M6MJsQ	V842dH
E2y429	v5yTz2	pe8Mc9	12N7qQ	gwU396	4rfHM1	n649EB	825AlW	ierE82	13cBtg
9518tM	g3Sgfp	A81e09	pnhSV6	dF92Xz	6O7r35	ZS2t6U	P8v4R2	5kJ970	o322Z0
nIxV2j	8sUjWY	JnU2PJ	n8rJz2	374Pod	A30K3h	PMBb4R	k6wV89	66Qz0G	UzL2Bl
pJ8390	U52DuP	39zJ77	7t55K5	7a3U66	W4637s	pTW89D	e4126V	5u64P1	2P9A2v
AYE91k	646Zuv	K0Jl61	ukG53X	2cxBh6	64e75H	PQx3FL	i09yBU	TjSD32	h19U47
LFvI8T	9Ggkum	187Lk7	3n1E13	luYLO7	3I2XjH	12pN57	w18EsS	CI45w7	2dUxsv
047d1H	rEx8us	Tz4K7H	84n1fD	Sj0yAZ	JJ86yp	4hQ487	I46vI5	182yEK	1T4yme
c6ZpO3	w5Ikk9	x6b2U6	m7G20M	9Wb689	35E78h	8dW818	48dd4W	38UDlf	7G8n24
H1tE1F	64Q9c2	ZFWVw7	2mPgqB	a79tnX	47At96	4RJUXj	ae9fLk	4w5C32	56J44b
13pXyq	W7832q	4YiTKh	9wTtML	rUwuf4	63Q12q	fNA7Zz	Ea9rU3	4B707i	E7091g
hI0f46	S88GRt	C9627d	1989Gd	28L59z	2J5e31	7a03nJ	1zvaSL	x962V7	Vat5r6
AR8f81	dDmw3k	hV3n96	zeq2K2	1952Kl	85Q17c	ZJCo60	HE1sIq	Hr61v5	EtIV4G
S40D3t	4NM4s9	l967G1	473KzQ	5u5RbC	Me356X	mGQE29	CYrTn8	3mpIg8	7P5c71