String 类的常用方法

1，求长判相等：

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		String string =reader .next();
		int n=string .length();
		System.out.println(n);
		String string2 =reader.next();
		if(string .equals(string2))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
		reader.close();
		
	}
}

akkhhhjjkk
10
akkhhhjjkk
YES

2： 判头判尾是否相同

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		String string =reader .next();
		String string2 =reader.next();
		if(string .startsWith(string2))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
		reader.close();
		if(string .endsWith(string2))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
	}
}

aaabbb
aaa
YES

3：判断当前字符串的某个位置间的子字符串和另一个字符串是否相等

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		String string =reader .next();
		String string2 =reader.next();
		if(string .regionMatches(0, string2, 0, 3))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
		reader.close();
	}
}

eeeccc
eee
YES

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		String string =reader .next();
		String string2 =reader.next();
		if(string .regionMatches(2, string2, 0, 3))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
		reader.close();
	}
}

eeccceee
ccc
YES

该方法的重载方法：（忽略大小写）

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		String string =reader .next();
		String string2 =reader.next();
		if(string .regionMatches(true,0, string2, 0, 3))
		{
			System.out.println("YES");
		}
		else
		{
			System.out.println("NO");
		}
		reader.close();
	}
}

aaaVVV
AAA
YES

4 判断两个字符串按字典序列比较大小

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .next();
		String string2 =reader.next();
		if(string .compareTo(string2)==0)
		{
			System.out.println("YES");
		}
		if(string .compareTo(string2)>0)
		{
			System.out.println("NO I LOVE");
		}
		if(string .compareTo(string2)<0)
		{
			System.out.println("NO I DONT LOVE");
		}
		}
		reader.close();
	}
}

aaaccc
aaaccc
YES
abcde
b
NO I DONT LOVE
abcde
abbde
NO I LOVE

5 判断当前字符串是否包含另一个字符串

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .next();
		String string2 =reader.next();
		if(string .contains(string2))
		{
			System.out.println("I LOVE YOU");
		}
		else
		{
			System.out.println("I DONT LOVE YOU");
		}
		}
		reader.close();
	}
}

aaaaaa
ccc
I DONT LOVE YOU
aaaa
a
I LOVE YOU

6 从开端和当前位置分别检索有无此字符串：

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .next();
		String string2 =reader.next();
		int n=string .indexOf(string2);
		if(n!=-1)
		{
			System.out.println(n);
		}
		else
		{
			System.out.println("NO");
		}
		}
		reader.close();
	}
}

aaaaaa
cccccc
NO
aaaaaa
a
0
aaaaaa
bbbbaa
NO
abcdabd
abd

从当前位置开始检索：

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .next();
		String string2 =reader.next();
		int n=string .indexOf(string2,4);
		if(n!=-1)
		{
			System.out.println(n);
		}
		else
		{
			System.out.println("NO");
		}
		}
		reader.close();
	}
}

ILOVEYOU
YOU
5
ILOVEYOU
LOVE
NO

7 获取模式串的子串：

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .next();
		String string2 =string.substring(1,5);
		System.out.println(string2);
		}
		reader.close();
	}
}

ILOVEYOU
LOVE

8将一个字符串去掉空格（仅限前后）：

import java.util.*;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner reader =new Scanner(System.in);
		while(reader.hasNext())
		{
		String string =reader .nextLine();
		String string2 =string.trim();
		System.out.println(string2);
		}
		reader.close();
	}
}

I LOVE YOU
I LOVE YOU
 I LOVE YOU （后面有空格）
I LOVE YOU