Java习题集3 - 图文

float math,english,sum; float f(float k1,float k2) {

sum=k1*math+k2*english; return sum; } }

public class Average {

Student wanghong,lihong;

public static void main(String args[]) {

wanghong=new Student(); lihong=new Student(); wanghong.math=60.0f; wanghong.english=80f; lihong.math=70.0f; lihong.english=90.0f;

wanghong.sum=wanghong.f(2.0f,2.0f); lihong.sum=lihong.f(2.0f,2.0f);

System.out.println(\

System.out.println(\ } }

答：运行结果为：lihong sum=320.0 wanghong sum=280.0

17、

import java.awt.*; class Chengji {

float f(float x,float y) {

return x*y; } }

class Xiangjia extends Chengji {

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//重写父类的f方法

float f(float x,float y) {

return x+y; } }

public class Class1 {

Xiangjia sum;

public static void main(String args[]) {

sum=new Xiangjia();

System.out.println(\

//此处对象sum是调用自已的方法f,得到两数的和. } }

答：运行结果为：sum=10.0

18、

public class Class1 {

float a[];

public static void main(String args[]) {

a=new float[5]; a[0]=23.9f; a[1]=34.9f; a[2]=45f; a[3]=56.98f; a[4]=100f;

System.out.println (\ System.out.println (\ System.out.println (\ System.out.println (\ System.out.println (\ } }

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答：运行结果为： a[0]=23.9 a[1]=34.9 a[2]=45.0 a[3]=56.98 a[4]=100.0

19、

public class Class1 {

String tom=\ int x,y,z;

public static void main(String args[]) {

x=tom.indexOf(\

y=tom.indexOf(\ z=tom.indexOf(\ g.setColor(Color.red);

System.out.println(\ } }

答：运行结果为：2:7:13

20、

public class Class1 {

String jerry=\

public static void main(String args[]) {

s1=jerry.substring(2); s2=jerry.substring(2,5); g.setColor(Color.blue); System.out.println (s1); System.out.println (s2);

System.out.println (jerry.substring(jerry.indexOf(\ } }

答：运行结果为：love Tom

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lov

love Tom

21、

import java.util.*; import java.awt.*; public class Class1 {

public static void main (String[] args) throws java.io.IOException {

String s1=\ String s2=\

StringTokenizer fenxi_1=new StringTokenizer(s1,\空格和逗号做分隔符

StringTokenizer fenxi_2=new StringTokenizer(s2,\空格和问号做分隔符

int n1=fenxi_1.countTokens(); int n2=fenxi_2.countTokens(); while(fenxi_1.hasMoreTokens()) {

String s=fenxi_1.nextToken(); System.out.print(s+? ?); }

System.out.println();

System.out.println(\有单词:\个\ while(fenxi_2.hasMoreTokens()) {

String s=fenxi_2.nextToken(); System.out.print(s+? ?); }

System.out.println();

System.out.println(\有单词:\个\ int i;

i=System.in.read(); } }

答：运行结果为：I am Geng.X.Y she is my girlfriend s1有单词：7个

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