String类概述

String类概述

测试类：

package com.ax.test;

public class TestCreateStringObject {
    public static void main(String[] args) {
        String dec = "喜羊羊";
        String newDec = new String(dec);
        System.out.println("是否具有相等的字符序列:"+(dec.equals(newDec)));//true
        System.out.println("是否具有同一个引用:"+(dec == newDec));//false
    }
}

String类常用方法1

public char charAt(int index)

public int compareTo(String target)

public boolean equals(String target)

public boolean equalslgnoreCase(String target)

public boolean endsWith(String suffix)

public boolean startsWith(String prefix)

package com.ax.test;

public class TestStringMethods {
    public static void main(String[] args) {
        String name = "懒羊羊";

        //charAt 方法，给定的索引不能超出字符串序列索引，否则出现异常
        char res = name.charAt(2);
        System.out.println(res);
        //compareTo 方法，如果当前面对象大于后面对象则返回正数，小于则返回负数，等于返回0
        String a = "abcdefg";
        String b = "abceefg";
        System.out.println(a.compareTo(b));

        //测试是否以某个字符串正则表达式所描述的为开头或结尾的方法

        String email = new String("abc@163.com");
        System.out.println(email+"是否以.com结尾的"+email.endsWith(".com"));
    }
}

String类常用方法2

public String trim()

public int indexOf(int ch)

public int indexOf(int ch,int fromIndex)

public int indexOf(String target)

public int indexOf(String target,int fromIndex)

public int length()

package com.ax.test;

public class TestStringMethods {
    public static void main(String[] args) {
        String name = "懒羊羊";

        //charAt 方法，给定的索引不能超出字符串序列索引，否则出现异常
        char res = name.charAt(2);
        System.out.println(res);//羊
        //compareTo 方法，如果当前面对象大于后面对象则返回正数，小于则返回负数，等于返回0
        String a = "abcdefg";
        String b = "abceefg";
        System.out.println(a.compareTo(b));//-1

        //测试是否以某个字符串正则表达式所描述的为开头或结尾的方法

        String email = new String("abc@163.com");
        System.out.println(email+"是否以.com结尾的"+email.endsWith(".com"));//abc@163.com是否以.com结尾的true

        //去掉空格的trim方法
        String srcStr = "    懒羊羊";
        System.out.println(srcStr.length());//7
        String newSrcStr = srcStr.trim();
        System.out.println("新字符串:"+newSrcStr);//新字符串:懒羊羊
        System.out.println("原字符串:"+srcStr);//原字符串:    懒羊羊

        //String对象的indexOf查找目标字符或字符串方法
        int index = email.indexOf('@');
        System.out.println("@符号的位置索引:"+index);//3
    }
}

String类常用方法3

public String[] split(String regex)

public String substring(int beginIndex)

public String substring(int beginIndex,int endIndex)

public char[] toCharArray()

public String toLowerCase()

public String toUpperCase()

package com.ax.test;

import java.util.Locale;

public class TestStringMethods1 {
    public static void main(String[] args) {
        //字符串的分割方法
        String sheep = "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊";
        String [] sheepArray = sheep.split("喜羊羊");
        System.out.println(sheepArray.length);//2

        //提取字符串的sustring方法,注意不能超出原串的索引
        String str1 = new String("我是一只快乐的小羊");
        System.out.println(str1.substring(3));//只快乐的小羊
        System.out.println(str1.substring(0,4));//我是一只

        //将字符串转化为char型数组的tocharArray
        char [] chars = "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊".toCharArray();
        System.out.println(chars.length == "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊".length());//true
        System.out.println("abcdefg".toUpperCase());//转换为大写ABCDEFG
        System.out.println("abCDefg".toLowerCase());//转换为小写abcdefg

        //字符串包含方法

        String name = "喜羊羊,懒羊羊";
        System.out.println(name.contains("懒羊羊"));//true
    }
}

String类常用方法4

public String replace(char oldChar,char newChar)

public String replace(String oldChar,String newChar)

public static String valueOf(Object obj)

实体类：

package com.ax.pojo;

public class Users {
    public String name ;

    public Users(String name) {
        this.name = name;
    }

}

测试类：

package com.ax.test;

import com.ax.pojo.Users;

import java.util.Locale;

public class TestStringMethods1 {
    public static void main(String[] args) {
        //字符串的分割方法
        String sheep = "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊";
        String [] sheepArray = sheep.split("喜羊羊");
        System.out.println(sheepArray.length);//2

        //提取字符串的sustring方法,注意不能超出原串的索引
        String str1 = new String("我是一只快乐的小羊");
        System.out.println(str1.substring(3));//只快乐的小羊
        System.out.println(str1.substring(0,4));//我是一只

        //将字符串转化为char型数组的tocharArray
        char [] chars = "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊".toCharArray();
        System.out.println(chars.length == "懒羊羊,喜羊羊,美羊羊,沸羊羊,暖羊羊".length());//true
        System.out.println("abcdefg".toUpperCase());//转换为大写ABCDEFG
        System.out.println("abCDefg".toLowerCase());//转换为小写abcdefg

        //字符串包含方法

        String name = "喜羊羊,懒羊羊";
        System.out.println(name.contains("懒羊羊"));//true


        //字符串替换方法
        String color = "blue";
        System.out.println(color.replace("u","l"));//blle
        System.out.println(color.replace("blue","yellow"));//yellow

        //静态方法构建字符串对象
        String dest = String.valueOf(new Users("喜羊羊"));
        System.out.println(dest);//com.ax.pojo.Users@16d3586
        System.out.println(String.valueOf(new Boolean(true)));//true
        
    }
}