文章目录
String
1.String的构造方法
1)String(String original):把字符串数据封装成字符串对象
2)String(char[] value):把字符数组的数据封装成字符串对象
3)String(char[] value, int index, int count):把字符数组中的一部分数据封装成字符串对象
2.String 类代表字符串。
Java 程序中的所有字符串字面值(如 “abc” )都作为此类的实例实现。
string特点:
2. 1:字符串内容不可变
2 .2:字符串可共享
2 .3:字符串效果上相当于一个char[],但实际底层存储的是byte()
2.4 常用三种构造方法:
public String()
public String(char[])
public String(byte())
3equals()
方法用于将字符串与指定的对象比较。
String 类中重写了 equals() 方法用于比较两个字符串的内容是否相等。
程序代码及结果
package demo01;
/*
* String 类代表字符串。Java 程序中的所有字符串字面值(如 "abc" )都作为此类的实例实现。
* string特点:
* 1:字符串内容不可变
* 2:字符串可共享
* 3:字符串效果上相当于一个char[],但实际底层存储的是byte()
* 常用三种构造方法:
* public String()
*public String(char[])
*public String(byte())
*/
public class Demo01String {
public static void main(String[] args) {
String str1=new String();//小括号留空,没有内容
System.out.println("第一个字符串"+str1);
System.out.println("================");
char[] chararray= {
'a','b','c','d'};
System.out.println(chararray);
String str2=new String(chararray);
System.out.println(str2);
System.out.println("================");
byte[] bytearray= {
97,98,99};
System.out.println(bytearray);
String str3=new String(bytearray);
System.out.println(str3);
System.out.println("================");
String str4="class5";
System.out.println(str4);
}
}
package demo01;
public class Demo02StringPoo {
public static void main(String[] args) {
String str1="a,b,c";
String str2="a,b,c";
System.out.println(str2);
char[] chararray= {
'a','b','c'};
String str3=new String(chararray);
System.out.println(str1==str2);//第一个和第二个地址一样
System.out.println(str1==str3);
System.out.println(str2==str3);
str2="c,d,e";
System.out.println(str2);
}
}
package demo02;
public class Demo01StringEquals {
public static void main(String[] args) {
String str1="zhoumin";
String str2="zhoumin";
System.out.println(str2);
char[] chararray= {
'z','h','o','u','m','i','n'};
String str3=new String(chararray);
System.out.println(str1.equals(str2));//第一个和第二个地址一样
System.out.println(str2.equals(str3));
System.out.println(str1.equals(str3));
System.out.println(str1.equals("zhoumin"));
System.out.println("zhoumin".equals(str1));
System.out.println("================");
String str4=null;
//System.out.println(str4.equals("zhoumin"));
System.out.println("zhoumin".equals(str4));
String str5="zhoumin";
System.out.println("Zhoumin".equals(str4));
System.out.println("================");
System.out.println("zhoumin".equalsIgnoreCase(str5));
}
}
package demo02;
public class Demo02StringGet {
public static void main(String[] args) {
//字符串长度
int length="zhouminzhenmeili".length();
System.out.println("字符串长度"+length);
//字符串拼接
String str1="zhoumin";
String str2="zhenhaokan";
String str3=str1.concat(str2);
System.out.println(str1);//zhoumin
System.out.println(str2);//zhenhaokan
System.out.println(str3);//zhouminzhenhaokan
//获得制定索引字符串位置
char ch="Hello".charAt(4);
System.out.println("0号索引位置的字符是"+ch);
String origan1="HelloworldHelloworldHelloworld";
int index=origan1.indexOf("llo");
}
}
package demo02;
public class Demo02StringSplit {
public static void main(String[] args) {
String str1="aaa bbb bccc";
String[] array1=str1.split(" ");
for(int i=0;i<array1.length;i++) {
System.out.println(array1[i]);
}
}
}
package demo02;
public class Demo03SubString {
public static void main(String[] args) {
String str1="Helloclass5";
String str2=str1.substring(5);
System.out.println(str1);
System.out.println(str2);
String str3=str1.substring(2,5);
System.out.println(str3);
}
}
package demo03;
import java.util.Arrays;
public class Demo01Arrays {
public static void main(String[] args) {
int[] intArray= {
10,20,30};
System.out.println(intArray);
String intStr=Arrays.toString(intArray);
System.out.println(intStr);
int[] array1= {
3,3,5,7,9,3,5,6};
System.out.println(Arrays.toString(array1));
Arrays.sort(array1);
System.out.println(Arrays.toString(array1));
String[] array2= {
"aaa","sss","nnn"};
Arrays.sort(array2);
System.out.println(Arrays.toString(array2));
}
}
package demo03;
public class Demo02Math {
public static void main(String[] args) {
//去绝对值
System.out.println(Math.abs(3.14));
System.out.println(Math.abs(0));
System.out.println(Math.abs(-3.14));
System.out.println("================");
//向上取整
System.out.println(Math.abs(3.91));
System.out.println(Math.abs(3.5));
System.out.println(Math.abs(3.00001));
System.out.println("================");
//向下取整
System.out.println(Math.abs(3.91));
System.out.println(Math.abs(3.5));
System.out.println(Math.abs(3.00001));
System.out.println("================");
System.out.println(Math.round(20.4));
System.out.println(Math.round(3.5));
}
}
package demo04;
public class Demo01StaticFiled {
public static void main(String[] args) {
Student one =new Student("周敏",19);
one.setRoom("教室3306");
System.out.println(one.getName()+" "+one.getAge()+" "+one.getRoom());
Student two =new Student("范丞丞",20);
System.out.println(two.getName()+" "+two.getAge()+" "+two.getRoom());
}
}
package demo04;
public class Demo01StaticMethod {
public static void main(String[] args) {
MyClass obj=new MyClass();
obj.method();//普通方法 必须通过对象调用
obj.methodStatic();//通过对象调用
MyClass.methodStatic();//通过类直接调用 推荐
}
}
package demo04;
public class MyClass {
int num;
static int numstatic;
public void method() {
System.out.println("这是成员方法");
}
public static void methodStatic() {
System.out.println("这是静态方法");
}
}
package demo04;
public class Student {
private int id;
private String name;
private int age;
private static String room;
public Student( String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public static String getRoom() {
return room;
}
public static void setRoom(String room) {
Student.room = room;
}
}