java之day6

package day6;import java.util.Arrays;public class StringTest {public static void main(String[] args) {// &＃61;&＃61; 比较的是两个数据的大小//基本数据类型的存储区域在栈中&＃xff0c;每一个数据都是相互独立存在的int i &＃61; 5;int j &＃61; 5;System.out.println(i&＃61;&＃61;j);//数组是引用数据类型&＃xff0c;//数组占用两块空间&＃xff1a;栈和堆//栈中存放数组数据在堆中存在的首地址&＃xff08;数组名&＃xff09;//堆中存放的是数组数据int arr1[] &＃61; new int[2];arr1[0] &＃61; 1;arr1[1] &＃61; 2;int arr2[] &＃61; new int[2];arr2[0] &＃61; 1;arr2[1] &＃61; 2;System.out.println(arr1&＃61;&＃61;arr2);System.out.println(Arrays.equals(arr1, arr2));//普通的声明字符串的方法&＃xff0c;只会在字符串常量池里开辟空间&＃xff1b;//并且在开辟之前&＃xff0c;会检查字符串常量池里是否已经存在&＃xff1b;//相同的数据&＃xff0c;如果有&＃xff0c;直接指向已经存在的数据&＃xff0c;如果没有&＃xff0c;会在字符串常量池中开辟一个新的空间&＃xff1b;String s &＃61; "ccy";String s2 &＃61; "ccy";System.out.println(s&＃61;&＃61;s2);//在堆里开辟一个空间&＃xff0c;存放内容&＃xff0c;然后检查字符串常量池里又没有&＃xff0c;没有就在池里开辟一个空间存放jerehString s3 &＃61; new String("jereh");String s4 &＃61; new String("jereh");System.out.println(s3 &＃61;&＃61; s4);String s6 &＃61; new String("jredu");String s5 &＃61; "jredu";System.out.println(s5 &＃61;&＃61; s6);}
}

package day6;public class Demo03 {//.concat() 链接字符串public static void main(String[] args) {String string &＃61; new String("nihao");String name &＃61; new String("zhangsan");String abc &＃61; string.concat(name);System.out.println(abc);}
}

package day6;import org.omg.CORBA.INTERNAL;import day52.shuzu;public class Demo04 {public static void main(String[] args) {String a &＃61; new String("asdf.java");//indexOf() 获取字符串中某个字符或字符串出现的位置System.out.println(a.indexOf("a"));//lastIndesOf() 获取字符串中某个字符或字符串最后一次出现的位置System.out.println(a.lastIndexOf("a"));//substring(index)从指定位置(包含)开始截取字符串&＃xff0c;知道最后一个String newA &＃61; a.substring(4);System.out.println(newA);int index &＃61; a.indexOf(".");String newA2 &＃61; a.substring(index&＃43;1);System.out.println(newA2);//从指定索引开始&＃xff08;包含&＃xff09;&＃xff0c;到指定索引结束&＃xff08;不包含&＃xff09;String newA3 &＃61; a.substring(2,4);System.out.println(newA3);//trim()去前后空格String s2 &＃61; " 杰 瑞 教 育 ";String newS4 &＃61; s2.trim();System.out.println(newS4);}}

package day6;public class Demo06 {public static void main(String[] args) {//分隔String words &＃61; "长亭外 古道边 芳草碧连天 晚风拂柳笛声残 夕阳山外山";String[] printword &＃61; new String[100];System.out.println("***原歌词格式***\n" &＃43; words);System.out.println("\n***拆分后歌词格式***");printword &＃61; words.split(" ");for (int i &＃61; 0; i ) {System.out.println(printword[i]);}}
}

package day6;public class Demo07 {public static void main(String[] args) {//StringBuffer//append() 用来向stringBuffer追加内容的StringBuffer sb &＃61; new StringBuffer("QWER");int num &＃61; 110;StringBuffer sb1 &＃61; sb.append("qwerty");System.out.println(sb1);StringBuffer sb2 &＃61; sb1.append("qwerty");System.out.println(sb2);StringBuffer sb3 &＃61; sb2.append(num);System.out.println(sb3);//String ---> StringBufferStringBuffer s &＃61; new StringBuffer("qwer");//StringBuffer ---> String
sb.toString();}
}

package day6;import java.util.Scanner;public class Demo08 {public static void main(String[] args) {//StringBuffer insert(索引index&＃xff0c;方法content)方法Scanner scanner &＃61; new Scanner(System.in);System.out.println("qingshuru");String string &＃61; scanner.next();StringBuffer buffer &＃61; new StringBuffer(string);for (int i &＃61; buffer.length()-3; i > 0; i-&＃61;3) {buffer.insert(i, ",");}System.out.println(buffer);scanner.close();}
}

package day6;import java.util.Arrays;public class Test {public static void main(String[] args) {String string &＃61; "爱你&＃xff0c;爱我&＃xff0c;爱她&＃xff0c;爱中国&＃xff01;爱";string &＃61; " "&＃43;string&＃43;" ";int length &＃61; string.split("爱").length-1;System.out.println(length);}
}

package day61;public class Test {//全局变量有初始值//局部变量没有初始值int i;//OR下面那个int i &＃61; 0;public void check(){// int i &＃61;0;
System.out.println(i);}public static void main(String[] args) {Test test &＃61; new Test();test.check();}
}