Java:实例

1. Java开始

public class HelloWorld{
public static void main(String[] args){
System.out.println("Hello world.");
}
}

//编译，执行
$ javac HelloWorld.java
$ java HelloWorld
Hello world.

2. 字符串处理

2.1 字符串比较

public class StringCompare{
public static void main(String[]  args){
String str = "Hello World.";
String another_str = "hello world.";
Object objStr = str;

System.out.println(str.compareTo(another_str));
System.out.println(str.compareToIgnoreCase(another_str));
System.out.println(str.compareTo(objStr.toString()));

}
}

// $ java StringCompare
-32
0
0

2.2 字符串查找

public class StringCompare2{
public static void main(String[]  args){
String str_orig = "Hello world, Hello reader.";

int last_index = str_orig.lastIndexOf("Hello");
if(last_index == -1){
System.out.println("Not Found");
}
else{
System.out.println("Last occurrence of index is " + last_index);
}

}
}

// Last occurrence of index is 13

2.3 删除字符串中一个字符

public class RemoveChar{
public static void main(String[]  args){
String str = "This is a line.";

System.out.println(removeChar(str, 3));
}

public static String removeChar(String s, int pos){
String newStr = s.substring(0, pos) + s.substring(pos + 1);
return newStr;
}
}

//$ javac RemoveChar.java
//$ java RemoveChar
Thi is a line.

2.4 字符串替换

public class StringReplace{
public static void main(String[] args){
String str = "Hello World. Hello";
System.out.println(str.replace('H', 'W'));
System.out.println(str.replaceFirst("He", "We"));
System.out.println(str.replaceAll("He", "We"));
}
}

//
Wello World. Wello
Wello World. Hello
Wello World. Wello

2.5 字符串反转

public class StringReverse{
public static void main(String[]  args){
String str = "Hello World";
String reverse = new StringBuffer(str).reverse().toString();

System.out.println("Reverse string is :" +  reverse);

}

}

//
Reverse string is :dlroW olleH

2.6 字符串搜索

String str = "Hello, Java.";
int intIndex = str.indexOf("Hello");
System.out.println(intIndex);
// 0

2.7 字符串分隔

String str1 = "www.baidu.com";
String[] temp;
String delimter = "\\.";  // . 需要转义
temp = str1.split(delimter);
for(String s : temp){
System.out.println(s);
}

//
www
baidu
com

2.8 字符串大小写转换

String str2 = "www.baidu.com";
String strUp = str2.toUpperCase();
String strLower = strUp.toLowerCase();
System.out.println("str2 : " + str2);
System.out.println("strUp : " + strUp);
System.out.println("strLower : " + strLower);
//
str2 : www.baidu.com
strUp : WWW.BAIDU.COM
strLower : www.baidu.com