随机密码生成

import java.util.Random;

public class RandomPassword {
    private int length = 8;   	// password length
    private int numLen = 2;     // count of numbers
    private int nonABNumLen = 1;// count of special character

    /**
     * get an alphabeta
     * @return
     */
    private char getAB() {
        Random rand = new Random();
        int ri = rand.nextInt(52);
        char c = 0;
        if (ri < 26) {
            c = (char) (65 + ri);
        } else {
            c = (char) (97 + ri - 26);
        }
        return c;
    }

    /**
     * get a num
     * @return
     */
    private char getNum() {
        Random rand = new Random();
        int ri = rand.nextInt(10);
        char c = (char) (48 + ri);
        return c;
    }

    /**
     * get a non num / non abc char
     * @return
     */
    private char getNonABNum() {
        Random rand = new Random();
        int total = (47 - 32) + (64 - 57) + (96 - 90) + (126 - 122);	//total nonABNUM characters
        int ri = rand.nextInt(total);
        char c = 0; 
        if (ri < (47 - 32)) {
        	c = (char) (ri + 32 + 1); 
        } else if (ri < (47 - 32)+(64 - 57)) {
        	c = (char) (ri - (47 - 32) + 57 + 1); 
        } else if (ri < (47 - 32)+(64 - 57) + (96 - 90)) {
        	c = (char) (ri - (47 - 32) -(64 - 57) + 90 + 1 );
        } else {
        	c = (char) (ri - (47 - 32) -(64 - 57) - (96 - 90) + 122 + 1 );
        }
        return c;
    }

    /**
     * Generate the password chars array
     */
    public String password() {
        char[] pwd = new char[length];
        
        // generate the pwd chars
        for (int i = 0; i < length; i++ ) { 
        	if (i < length -numLen -nonABNumLen) {
        		pwd[i] = getAB(); 
        	} else if (i < length -nonABNumLen ) {
        		pwd[i] = getNum(); 
        	} else {
        		pwd[i] = getNonABNum(); 
        	}
        }
        
        // randomly shuffle pwd char array - Fisher–Yates shuffle
        Random rand = new Random();
        for (int i = length - 1; i > 0; i --) { 
        	int j = rand.nextInt(i + 1);
        	// swap char[i] and char[j]
        	char c = pwd[j];
        	pwd[j] = pwd[i]; 
        	pwd[i] = c; 
        }
        return new String(pwd);
    }
    
    /**
     * Test
     * @param args
     */
    public static void main(String[] args) {
        RandomPassword rp = new RandomPassword ();
        for (int i = 0; i< 20; i++) {
        	System.out.println ("Random Password: " + rp.password());
        }
    }
}

某次运行结果：

Random Password: "f1iiu9E
Random Password: X:9LT9UX
Random Password: BO7CQ'U4
Random Password: Esp^N00r
Random Password: f51BpT^D
Random Password: d2)mRPy0
Random Password: m0Ww^8aa
Random Password: FwV)RQ22
Random Password: 1_9hRtSt
Random Password: Q9m1YMM=
Random Password: 7cN#Jo7o
Random Password: 3oa7s^OO
Random Password: i(OB6Xz8
Random Password: VL6h2z^j
Random Password: (eVqu9p9
Random Password: ~DGGS80o
Random Password: [2lp4xlL
Random Password: #vs0sHv9
Random Password: Lp0XX2]L
Random Password: (POo9jC7