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【示例2】给变量赋值的演示。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleTwo {public static void main(String[] args) {int a, b;a = 1;System.out.println("a="+a);a = a + 1;System.out.println("a="+a);b = a + 1;System.out.println("b="+b);a = b + 2;System.out.println("a="+a);}}

【示例3】变量初始化的演示。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleThree {public static void main(String[] args) {byte a = 0x78;int b = 3;float c = 1.23f;double d = 3.23;boolean e = false;char f = 'A';System.out.println("convert to decimal: a="+a);System.out.println("b="+b);System.out.println("c="+c);System.out.println("d="+d);System.out.println("e="+e);System.out.println("f="+f);}}

【示例4】变量的作用域演示。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleFour {static int x=5;public static void main(String[] args) {int y=23;System.out.println("x="+x);System.out.println("y="+y);m(6);}static void m(int z){System.out.println("z="+z);System.out.println("x="+x);}}

【示例5】算术运算。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleFive {public static void main(String[] args) {int a=3,b=5,c=5;System.out.println("initial value:a=3,b=5,c=5");System.out.println("b/a="+b/a);System.out.println("c%a="+c%a);System.out.println("-a="+(-a));System.out.println("b++="+(b++)+", "+"b="+b);System.out.println("++c="+(++c)+", "+"c="+c);}}

【示例6】逻辑运算。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleSix {public static void main(String[] args) {int x=1,y=2;int numOne=5,numTwo=5,numThree=5,numFour=5;boolean rOne,rTwo,rThree,rFour;rOne=x>y & numOne++==5;rTwo=x>y && numTwo++==5;rThree=x<y | numThree++==5;rFour=x<y || numFour++==5;System.out.println("logical value: rOne="+rOne+", numOne="+numOne);System.out.println("logical value: rTwo="+rTwo+", numTwo="+numTwo);System.out.println("logical value: rThree="+rThree+", numThree="+numThree);System.out.println("logical value: rFour="+rFour+", numFour="+numFour);}}

【示例7】比较3个数的大小，求出其中的最大值和最小值。

package javaone.programming.devcloud.chaptertwo;public class ChapterTwoExampleSeven {public static void main(String[] args) {int a=12,b=-23,c=34;int max,min,t;t=a>b?a:b;max=t>c?t:c;t=a<b?a:b;min=t<c?t:c;System.out.println("max="+max);System.out.println("min="+min);}}

课后习题

1. 编写一个程序，从控制台随机输入3个数，实现从小到大的排列顺序。

package javaone.programming.devcloud.chaptertwo;import java.util.Arrays;
import java.util.Scanner;public class ChapterTwoExerciseOne {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("Please enter three numbers: ");double[] numbers = new double[3];for (int i = 0; i < 3; i++) {numbers[i] = scanner.nextDouble();}Arrays.sort(numbers);System.out.println("sort numbers:");for (int i = 0; i < 3; i++) {System.out.print(numbers[i] + " ");}scanner.close();}}

2. 某银行提供了整存整取定期储蓄业务，存期分别为一年、两年、三年、五年。存期为一年，年利率为2.26%；存期为两年，年利率为2.7%；存期为三年，年利率为3.3%；存期为五年，年利率为3.6%。编写一个程序，输入存入的本金，计算并输出存一年、两年、三年、五年，到期取款时，银行应支付的本金和利息。

package javaone.programming.devcloud.chaptertwo;import java.util.Scanner;public class ChapterTwoExerciseTwo {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("Enter the deposit amount: ");double depositAmount = scanner.nextDouble();double rateOneYear = 2.26/100;double rateTwoYear = 2.7/100;double rateThreeYear = 3.3/100;double rateFiveYear = 3.6/100;double totalOneYear = depositAmount * (1 + rateOneYear);double totalTwoYear = depositAmount * Math.pow (1 + rateTwoYear, 2);double totalThreeYear = depositAmount * Math.pow (1 + rateThreeYear, 3);double totalFiveYear = depositAmount * Math.pow (1 + rateFiveYear, 5);System.out.printf("The total amount is : %.2f\n", totalOneYear);System.out.printf("The total amount is : %.2f\n", totalTwoYear);System.out.printf("The total amount is : %.2f\n", totalThreeYear);System.out.printf("The total amount is : %.2f\n", totalFiveYear);scanner.close();}}

3. 公司为员工提供了基本工资、房租津贴和餐补。其中，房租津贴为基本工资的20%，餐补为基本工资的30%。要求从控制台输入基本工资后，计算并输出实领工资。

package javaone.programming.devcloud.chaptertwo;import java.util.Scanner;public class ChapterTwoExerciseThree {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("Enter the basic salary: ");double basicSalary = scanner.nextDouble();double rentAllowance = basicSalary * 0.2;double foodAllowance = basicSalary * 0.3;double totalSalary = basicSalary + rentAllowance + foodAllowance;System.out.printf("RentAllowance: %.2f\n", rentAllowance);System.out.printf("FoodAllowance: %.2f\n", foodAllowance);System.out.printf("Total salary: %.2f\n", totalSalary);scanner.close();}}