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Common methods of the String class have?
String class is a string type, final modified type, underlying character array is immutable.
Acquisition method
String str = new String("123456789");
/**
* 获取信息
*/
System.out.println(""+str.length());//9，获取字符串长度
System.out.println(""+str.indexOf("2"));//1，获取指定字符在字符串中的位置
System.out.println(""+str.lastIndexOf("1"));//0,获取指定字符在字符串中最后一次出现的位置
System.out.println(""+str.charAt(3));//4，获取指定索引处的字符
Interception / Split string
/**
* 截取字符串
*/
System.out.println(""+str.substring(5));//6789，从指定索引处截取字符串
System.out.println(""+str.substring(5,7));//67，从指定索引处截取字符串
/**
* 按照指定字符分割字符串
*/
String[] chaStr=str3.split("9");
Judging method
/**
* 判断方法
*/
String str1 = new String("12345678AABn9");
System.out.println(""+str1.equalsIgnoreCase("12345678aaBn9"));//true;判断字符串内容是否相等,忽略大小写
System.out.println(""+str1.equals("123"));//false;判断字符串内容是否相等
System.out.println(""+str1.startsWith("123"));//true;判断字符串是否以123开始
System.out.println(""+str1.endsWith("123"));//false;判断字符串是否以123结束
Conversion process
/**
* 转化方法
*/
char[] strChar=str1.toCharArray();//转化为字符数组
System.out.println(""+str1.toLowerCase());//全部转化为小写
System.out.println(""+str1.toUpperCase());//全部转化为大写
Remove trailing spaces
/**
* 去掉首尾两端空格
*/
String str3=" 19898kjsd 09djkkkkkkj ";
System.out.println(str3.trim());//去掉首尾两端空格
Construction method
//封装空字符串对象
public String() {
this.value = "".value;
}
//将字符串数据封装成字符串对象
public String(String original) {
this.value = original.value;
this.hash = original.hash;
}
//将字符串数组转换成字符串
public String(char value[]) {
this.value = Arrays.copyOf(value, value.length);
}
//将字符数组的指定位置后的一定长度转换成字符串
public String(char value[], int offset, int count) {
if (offset < 0) {
throw new StringIndexOutOfBoundsException(offset);
}
if (count <= 0) {
if (count < 0) {
throw new StringIndexOutOfBoundsException(count);
}
if (offset <= value.length) {
this.value = "".value;
return;
}
}
// Note: offset or count might be near -1>>>1.
if (offset > value.length - count) {
throw new StringIndexOutOfBoundsException(offset + count);
}
this.value = Arrays.copyOfRange(value, offset, offset+count);
}
