执行流程_Thinginjava第四章，控制执行流程，练习题答案

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/**
* Created by Sandy.Liu on 2018/7/19.
* Thinking in java, version 4, chapter 4, practice 1
* Write a program to print from 1 to 100
*/
public class Chap4Prac1Printfrom1To100 {
public static void main(String[] args){
for(int i=1;i<=100;i++)
P.print(i+" ");
}
}

/**
* Created by Sandy.Liu on 2018/7/19.
* Thinking in java, chapter 4, practice 2
* Write a program which generating 25 random int numbers. Use if-else statement to classify it as
* greater than, less than or equal to a second randomly generated value.
*/
import java.util.*;
public class Chap4Prac2Generate25int {
public static void main(String[] args){
Random ran1 = new Random();
Random ran2 = new Random();
P.print("ran1: "+ran1);
P.print("ran2: "+ran2);
for(int i=0;i<25;i++){
int x = ran1.nextInt();
int y = ran2.nextInt();
if(x>y)
P.print(x+">"+y);
else if(x P.print(x+"<"+y);
else
P.print(x+"="+y);
}

}

}

import java.util.Random;

/**
* Created by Sandy.Liu on 2018/7/19.
* Thinking in java, version 4, chapter 4, practice 3
*/
import java.util.*;
public class Chap4Prac3 {
public static void main(String[] args){
Random ran3 = new Random();
Random ran4 = new Random();
while(true){
int x = ran3.nextInt(10);
int y = ran4.nextInt(10);
if(x>y)
P.print(x+">"+y);
else if(x P.print(x+"<"+y);
else
P.print(x+"="+y);

}}}

/**
* Created by Sandy.Liu on 2018/7/19.
* Thinking in java, version 4, chapter 4, practice 4
* Write a program using two nested for loops and the modules operator(%) to detect and print
* prime numbers
*/
public class Chap4Prac4For {
public static void main(String[] args){
for(int i = 1;i<100;i++){
int factor = 0;
for(int j=1;j<=i;j++){
if(i%j==0)
factor++;
}
if(factor<=2)
P.print(i);
}
}
}

/**
* Created by Sandy.Liu on 2018/7/19.
* Thinking in java, version 4, chapter 4, practice 5
*/
public class Chap4Prac5 {
static void binaryPrint(int q){
if(q==0) P.print(0);
else{
int nlz = Integer.numberOfLeadingZeros(q);
q<<=nlz;
for(int p=0;p<32-nlz;p++){
int n = (Integer.numberOfLeadingZeros(q)==0)?1:0;
System.out.println(n);
q<<=1;
}
}
P.print("");

}
public static void main(String[] args){
int i=1+4+16+64;
int j = 2+8+32+128;
int k = 0x100;
int m = 0;
P.print("Using Integer.toBinaryString(): ");
P.print("i = "+Integer.toBinaryString(i));
P.print("j = "+Integer.toBinaryString(j));
P.print("k = "+Integer.toBinaryString(k));
P.print("m= "+Integer.toBinaryString(m));
P.print("i & j = "+(i&j)+"="+Integer.toBinaryString(i&j));
P.print("i | j = "+(i|j)+"="+Integer.toBinaryString(i|j));
P.print("i ^ j = "+(i^j)+"="+Integer.toBinaryString(i^j));
P.print("~i = "+Integer.toBinaryString(~i));
P.print("~j = "+Integer.toBinaryString(~j));
P.print("Using binaryPrint():");
P.print("i = "+i+" = ");
System.out.print(i);
P.print("j = "+j+" = ");
System.out.print(j);
P.print("k = " + k + " = ");
System.out.print(k);
P.print("m = " + m + " = ");
System.out.print(m);
P.print("i & j = " + (i & j) + " = ");
System.out.print(i & j);
P.print("i | j = " + (i | j) + " = ");
System.out.print(i | j);
P.print("i ^ j = " + (i ^ j) + " = ");
System.out.print(i ^ j);
P.print("~i = " + ~i + " = ");
System.out.print(~i);
P.print("~j = " + ~j + " = ");
System.out.print(~j);
}
}

/**
* Created by Sandy.Liu on 2018/7/22.
* Thinking in java, version 4, chapter 4, practice 6
* Modify method test(), make them accept two other parameters begin and end, check if
* testval is between begin and end.
*/
public class Chap4Prac6 {
static int test(int testval, int begin, int end){
if (end P.print("end cannot be smaller than begin");
else if((testval <=end) &(testval>=begin))
return +1;
else if((testvalend))
return -1;
else
P.print("exceptional case");
return 13;
}
public static void main(String[] args){
test(10, 5,4);//begin P.print("case2: "+test(5,4,10));//begin P.print("case3: "+test(1,4,10));//testval P.print( "case4: "+test(5,5,6));//testval=begin
P.print("case5: "+test(5,1,5));//testval=end
P.print("case6: "+test(10,1,5));//testval>end
}
}

/**
* Created by Sandy.Liu on 2018/7/22.
* Thinking in java, version 4, chapter 4, practice 7
* Modify excise 1, use break to make program exists at value 99
*/
public class Chap4Prac7{
static void test(int x){
for(int i=0;i<=x;i++){
if(i==99)
break;
P.print(i);
}
}
static void test1(int x){
for(int i=0;i<=x;i++){
if(i==99)
return;
P.print(i);
}
}
public static void main(String[] args) {
test(100);
test1(1000);
}
}

/**
* Created by Sandy.Liu on 2018/7/23.
* Thinking in java, version 4, chapter 4, practice 8
* Create a switch statement that prints a message for each case, and put the switch inside a for loop
* to try each case. Put a break after each case and test it. And then remove the breaks and test again.
*/
public class Chap4Prac8Switch {
public static void main(String[] args){
for(int i = 0;i<100;i++){
switch (i){
case 0: P.print("zero");break;
case 1: P.print("one");break;
case 2: P.print("two");break;
case 3: P.print("three");break;
default: P.print(i+"more than three");
}
}
}
}

import java.lang.reflect.Array;
import java.util.ArrayList;

/**
* Created by Sandy.Liu on 2018/7/23.
* Thinking in java, version 4, chapter 4, practice 9
* A Fibonacci sequence is the sequence of numbers 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on,
* each number (from the third one ) is the sum of the previous two numbers.
* Create a method that takes a integer as parameter,and display all Fibonacci numbers starting
* from the beginning to the gave parameter. e.g., if you run javaFibonacci 5 (where Fibonacci
* is the name of the class) the output will be 1, 1, 2, 3, 5.
*/
public class Chap4Prac9Fibonacci {
static void gFib(int i) {
if (i <= 0)
P.print("please input a number bigger than 0");
int[] a = new int[i];
if (i <= 2) {
for (int k = 0; k a[k] = 1;
} else {
a[0] = 1;
a[1] = 1;
for (int j = 2; j a[j] = a[j - 2] + a[j - 1];
}
for (int m = 0; m System.out.print(a[m]);
}
P.print(" ");
}

public static void main(String[] args){
gFib(0);
gFib(1);
gFib(2);
gFib(5);
}

}

/**
* Created by Sandy.Liu on 2018/7/25.
* Thinking in java, version 4, chapter 4, practice 10
* A vampire number has an even number of digits and is formed by multiplying a pair of numbers
* containing half the number of digits of the result.
* The digits are taken from the original number in any order. Pairs of railing zeros are not
* allowed. Examples include:1260 = 21 * 60, 1827 = 21 * 87,
* 2187 = 27 * 81.
* Write a program that finds all the 4-digit vampire numbers.
*/
public class Chap4Prac10VaimpireNumber {
static int a(int i) {
return i / 1000;
}

static int b(int i) {
return (i % 1000) / 100;
}

static int c(int i) {
return ((i % 1000) % 100) / 10;
}

static int d(int i) {
return ((i % 1000) % 100) % 10;
}
static int com(int i, int j){
return i*10+j;
}
static void productTest(int i, int m, int n){
if(i==m*n){
P.print(i+"="+m+"*"+n);
}


}

public static void main(String[] args) {
for(int i = 1001;i<9999;i++){
productTest(i,com(a(i),b(i)),com(c(i),d(i)));
productTest(i,com(a(i),b(i)),com(d(i),c(i)));
productTest(i,com(a(i),c(i)),com(b(i),d(i)));
productTest(i,com(a(i),c(i)),com(d(i),b(i)));
productTest(i,com(a(i),d(i)),com(b(i),c(i)));
productTest(i,com(a(i),d(i)),com(c(i),b(i)));
productTest(i,com(b(i),a(i)),com(c(i),d(i)));
productTest(i,com(b(i),a(i)),com(d(i),c(i)));
productTest(i,com(b(i),c(i)),com(d(i),a(i)));
productTest(i,com(b(i),d(i)),com(c(i),a(i)));
productTest(i,com(c(i),a(i)),com(d(i),b(i)));
productTest(i,com(c(i),b(i)),com(d(i),a(i)));
}
}
}