String常用方法测试

String.Equals()使用方法

用来比较String两个对象所表示的字符串是否相同

public class StringEquals {

public static void main(String[] args) {

String s1=new String("Hello");

String s2=new String("Hello");

System.out.println(s1==s2);  //false

System.out.println(s1.equals(s2));   //true

String s3="Hello";

String s4="Hello";

System.out.println(s3==s4);       //true

System.out.println(s3.equals(s4));      //true

}

}

类的对象不能直接用==比较  比较的是两个String对象 不能用来比较对象和常量

对一些string 方法的测试 代码如下：

package demo;

//StringMisc.java

//This program demonstrates the length, charAt and getChars

//methods of the String class.

//

//Note: Method getChars requires a starting point

//and ending point in the String. The starting point is the

//actual subscript from which copying starts. The ending point

//is one past the subscript at which the copying ends.

import javax.swing.*;

public class Stringmisc {

public static void main( String args[] )

{

String s1, output,s2,s3;

char charArray[];

s1 = new String( "hello there" );

charArray = new char[ 5 ];

// output the string

output = "s1: " + s1;

// test the length method

output += "\nLength of s1: " + s1.length();

// loop through the characters in s1 and display reversed

output += "\nThe string reversed is: ";

for ( int i = s1.length() - 1; i >= 0; i-- )

output += s1.charAt( i ) + " ";

// copy characters from string into char array

//四个参数的含义

//1.被拷贝字符在字串中的起始位置

//2.被拷贝的最后一个字符在字串中的下标再加1

//3.目标字符数组

//4.拷贝的字符放在字符数组中的起始下标

s1.getChars( 0, 5, charArray, 0 );

output += "\nThe character array is: ";

for ( int i = 0; i < charArray.length;i++ )

output += charArray[ i ];

//test the replace method

s2 = s1.replace("e","o");         //replace方法完了转换后是返回一个新的对象，如果没有找到需要替换的字符串则返回原对象

output +="\nThe replace method result is:"+s2;

//test the toUpperCase and tpLowerCase

s2 = s1.toUpperCase();                        //toUpperCase 是把所有字符串变为大写

s3 = s1.toLowerCase();                        //toLowerCase 是吧所有字符串变为小写

output += "\nThe Upper is:"+s2;

output += "\nThe Lower is:"+s3;

//test The trim                                                //去掉字符串首位的空格

s2 = "      Hello There ";

s3 = "Hello There";

output += "\n Add The blank:"+s3.equals(s2);

s2 = s2.trim();

output += "\n after trim:" + s2.equals(s3);

//test the toCharArray                         //把字符串存入一个字符数组中

char array[] = s1.toCharArray();

output += "\ntoCharArray:";

for ( int i = 0; i < array.length;i++ )

output += array[ i ];

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Constructors",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

}